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[Abstract] Carrier-injection and the succeeding pre-channel-formation dynamics in organic thin-film transistor was observed using time-domain reflectometry. Having previously analyzed the depth-wise variation in the initial carrier-injection from the contact electrode to the channel region, we focus here on the succeeding pre-channel-formation dynamics. We demonstrate that a hole concentration in the semiconductor/gate insulator interface increases until its electrical capacitance is filled through contact and access resistances. Thereafter, the injected-hole dis-tribution gradually spreads. A reduction in both contact and access resistances is crucial not only for the static characteristics of the field effect transistor but also the dynamical response.

In recent years, organic flexible devices have been investigated extensively and sub-millimeter bending stability of organic thin film devices has been achieved by placing the active layer of the transistor on a neutral strain surface. Around the neutral strain surface, an organic thin film has a high bending durability because the in-plane tensile and compressive strain cancel each other. However, this type of highly flexible device is also destroyed or undergoes irreversible degradation when subjected to hard bending, and the breaking point is very difficult to detect experimentally. Therefore, we performed a finite element analysis of a flexible device and found a possible breaking point at the boundary between the contact electrode and the organic layer. This was the result of a strain concentration at the boundary due to the difference in Young's modulus of the organic semiconductor and Au. In addition, the shear stress is concentrated around the edge of the Au electrode. These results indicate that the most likely breaking point for this type of flexible transistor is a rupture of the organic layer at the interface with the Au electrode.

High throughput printing processes have been developed for the fabrication of organic flexible sheet devices. However, printing processes inevitably use toxic solvents to prepare inks of organic semiconductors. Here we propose a novel and complementary method for the preparation of flexible sheet electronics. A thermal pressing method has several advantages, such as (i) being solvent-free, (ii) resulting in flexible device with structural durability against bending, (iii) making simultaneous sealing available to prevent physical or atmospheric damage, and (iv) providing seamless application to roll-to-roll processes by combination with toner technology. We have demonstrated that the characteristics of a flexible organic field-effect transistor (OFET) fabricated by the thermal press process were not degraded during or after the bending test until a bending radius of 2 mm was achieved, which is sufficient for the concept of a rolled-up type flexible sheet display.

The effect of an applied gate electric field on the charge-order phase in β-(BEDT-TTF)2PF6 single-crystal field-effect transistor structure was observed at around room temperature by technical improvement with respect to sample preparation and electrical measurements. A relatively slight but systematic increase of the electrical conductance induced by the applied gate electric field and its temperature dependence was observed at around the metal-insulator transition temperature (TMI). The temperature dependence of the modulated electrical conductance demonstrated that TMI was shifted toward the lower side by application of a gate electric field, which corresponds to partial dissolution of the charge-order phase. The thickness of the partially dissolved charge order region was estimated to be several score times larger than the charge accumulation region.

We controlled the in-plane orientation of pentacene grains by graphoepitaxy using patterned amorphous-SiO2/Si substrates on which periodic grooves with slope edges had been formed. Pentacene crystals exhibited a clear tendency to align their b-axes perpendicular to the groove edges. Organic thin-film transistors were fabricated on the patterned and flat substrates and their transistor characteristics were compared. Although the patterned substrates increased the apparent mobility by only 10–20%, the number of grain boundaries with high potential barriers to carrier transport was reduced to half of that on flat substrates. This improvement is expected to enhance the response speed of pentacene organic thin-film transistors and suppress the sensitivity of their characteristics to the operating temperature.

We have demonstrated the inverter operation of stacked-structure CMOS devices using pentacene and ZnO as active layers. The fabrication process of the device is as follows: A top-gate-type ZnO thin-film transistor (TFT), working as an n-channel transistor, was formed on a glass substrate. Then, a bottom-gate-type pentacene TFT, as a p-channel transistor, was fabricated on top of the ZnO TFT while sharing a common gate electrode. For both TFTs, solution-processed silicone-resin layers were used as gate dielectrics. The stacked-structure CMOS has several advantages, for example, easy patterning of active material, compact device area per stage and short interconnection length, as compared with the planar configuration in a conventional CMOS circuit.

Extrinsic factors to disturb the carrier transport in pentacene field-effect transistors (FETs), as a representative of the high-mobility organic FETs (OFETs), have been comprehensively analyzed by using atomic-force-microscope potentiometry (AFMP), microscopic four-point-probe field-effect transistor (MFPP-FET) measurement, and other techniques. In the first part, by mainly using AFMP as a powerful tool to reveal the potential distribution in working OFETs, we show how and how much the formation of source/drain electrodes influences the apparent field-effect mobility both for top- and bottom-contact configurations. In the second part, we show the influence of irregular grain structures and regular grain boundaries. The films grown both at very low and high temperature ranges contain distinctive insulating parts, which make the apparent mobility very low. Within the moderate growth temperature range, the intrinsic field-effect mobility obtained by MFPP-FET measurement is proportional to the average grain size. This behavior is well explained by the polycrystalline model with the diffusion theory. According to the observations in this work, it is obvious that these extrinsic limiting factors must be carefully excluded to discuss the intrinsic mechanism of the carrier transport in OFETs.

Organic static induction transistor (OSIT) is a promising driving device for the displays, since it shows high-speed, high-power and low-voltage operation. In this study, the OSIT with fine gate electrode patterned by electron beam exposure were fabricated. We investigated the basic electrical characteristics of copper phthalocyanine OSIT and compared with the calculation results obtained by two-dimensional (2D) device simulator. The experimental results show that the gate modulation improved by reducing the electrode gap and on/off current ratio depends on the gate gap.

The control of the organic field-effect transistor characteristics is necessary to produce the integrated circuits using organic semiconductors. Variations in the poly (3-hexylthiophene) field-effect transistor characteristics upon post-treatment such as thermal treatment and voltage treatment in N 2 atmosphere have been investigated. The controllability and reproducibility of the threshold voltage and mobility were achieved as a result of the post-treatments.

We fabricated both thin film transistors (TFTs) and diodes using zinc oxide (ZnO) and pentacene, and investigated their basic characteristics. We found that field-effect mobility is influenced by the interface state between the semiconductor and dielectric layers. Furthermore, the complementary metal oxide semiconductor (CMOS) inverter using a p-channel pentacene field-effect transistor (FET) and an n-channel ZnO FET showed a relatively high voltage gain (8 - 12) by optimizing the device structure. The hybrid complementary inverters described here are expected for application in flexible displays, radio frequency identification cards (RFID) tags, and others.

By exploiting atomic-force-microscope potentiometry, we have studied the local potential distribution in the solutionprocessible tetrabenzoporphyrin (BP) bottom-contact thin-film transistor under controlled atmospheres. It is found that abrupt and big potential drops mainly appeared at the domain boundaries and cracks in the BP film when the transistor was under operation, indicating a dominant influence of domain boundary and crack on the device performance. Exposure of the device to O2 drastically reduced the potential drops at some boundaries, which is the main reason for the improved device performance by O2 exposure. 2008 Elsevier B.V. All rights reserved.

We report two types of integrated circuits based on a pentacene static-induction transistor (SIT), a pentacene thin-film transistor (TFT) and a zinc oxide (ZnO) TFT. The operating characteristics of a p-p inverter using pentacene SITs and a complementary inverter using a p-channel pentacene TFT and an n-channel ZnO TFT are described. The basic operation of logic circuits at a low voltage was achieved for the first time using the pentacene SIT inverter and complementary circuits with hybrid inorganic and organic materials. Furthermore, we describe the electrical properties of the ZnO films depending on sputtering conditions, and the complementary circuits using ZnO and pentacene TFTs.

For the realization of high-performance organic static induction transistors (OSITs), it is important to investigate the effect of a hole injection barrier at the interface between a pentacene films and a source electrode in OSITs. In this study, the OSITs based on pentacene films were fabricated on various metallic source electrodes with different work functions and on copper phthalocyanine (CuPc)/indium tin oxide (ITO) electrodes with different CuPc thicknesses. The hole injection barrier was affected by the work function of metallic source electrodes (ITO, Au, and Pt) and the thickness of CuPc (0, 3, and 5 nm). The obtained results demonstrate that a high on/off ratio is achieved when a hole injection barrier with a moderate height is formed at the interface. It was found that controlling the hole injection barrier is effective for improving the characteristics of OSITs.

Organic light-emitting diodes (OLEDs) combined with thin film transistor (TFT) are well suitable elements for low-cost, large-area active matrix displays. On the other hand, zinc oxide (ZnO) is a transparent material and its electrical conductivity is controlled from conductive to insulating by growth conditions. The drain current of ZnO FET is 180 µA. The OLED uses ZnO thin film (Al-doped) for the electron injection layer and is controlled by radio frequency (rf) and direct current (dc) sputtering conditions, such as Al concentration and gas pressure. Al concentration in the ZnO film and deposition rate have strong effects on electron injection. Furthermore, the OLED driven by ZnO FET shows a luminance of 13 cd/m2, a luminance efficiency of 0.7 cd/A, and an on-off ratio of 650.

Organic transistors have attracted considerable interest because they are lightweight, flexible, inexpensive, and highly efficient over large areas. As a result of these characteristics, organic transistors are expected to find use in a variety of applications, including electronic barcodes, displays, and sensors. Until now, their performance has been inferior to inorganic transistors because of their lower mobility values (typical mobility ranges are 1–10 and 500–10 000 cm Vs for organic and inorganic semiconductors, respectively). Attempts to enhance the performance of organic transistors have relied on decreasing the length and increasing the cross-sectional area through which the charge carriers travel. In the case of an organic thin-film transistor (OTFT), which is the most popular type of organic transistor (Fig. 1a), it is necessary to decrease the channel length and increase the channel width by fine patterning the source and drain electrodes. Nanometer-scale devices can be fabricated if state-of-the-art lithographic techniques are used prior to organic-film growth. However, this type of process is not practical for fabricating low-cost, largescale flexible electronics. One approach to resolving this issue is to employ a verticaltype transistor (Fig. 1b). The carrier pathway in a verticaltype transistor is perpendicular to the substrate, and the current is dispersed over a wide area in the device. A static induction transistor (SIT), which is frequently referred to as a solidstate triode, is one of the simplest vertical-type transistors. SITs were first developed using inorganic semiconductors

Organic thin-film transistors (OTFTs) are emerging as aninexpensive alternative to amorphous silicon devices becauseof their many attractive features, such as a simple fabricationprocess, low cost, and mechanical flexibility. Recently, the per-formance of OTFTs has been significantly improved by modi-fying the dielectric surface and/or source and drain (S/D) elec-trodes

A well-defined test structure of organic static-induction transistor (SIT) having regularly sized nano-apertures in the gate electrode has been fabricated by colloidal lithography using 130-nm-diameter polystyrene spheres as shadow masks during vacuum deposition. Transistor characteristics of individual nano-apertures, namely 'nano-SIT,' have been measured using a conductive atomic-force-microscope (AFM) probe as a movable source electrode. Position of the source electrode is found to be more important to increase current on/off ratio than the distance between source and gate electrodes. Experimentally obtained maximum on/off ratio was 710 (at V DS = -4V, V GS = 0 and 2V) when a source electrode was fixed at the edge of gate aperture. The characteristics have been then analyzed using semiconductor device simulation by employing a strongly non-linear carrier mobility model in the CuPc layer. From device simulation, source current is found to be modulated not only by a saddle point potential in the gate aperture area but also by a pinch-off effect near the source electrode. According to the obtained results, a modified structure of organic SIT and an adequate acceptor concentration is proposed. On/off ratio of the modified organic SIT is expected to be ∼100 times larger than that of a conventional one.

Static induction transistors (SITs) based on copper phthalocyanine (CuPc) were prepared and the dependence of static and transient characteristics on the edge features of the patterned Al gate electrode was studied. Devices having Al gate electrodes deposited with and without a gap between a shadow mask and the substrate were prepared. Devices prepared in the presence of the gap produces a thin transparent edge for the Al gate electrode which enhances the modulation of the drain current by the gate voltage. However, a repetitive slow transient of the drain current was observed for the devices using gap. This transient is considered to be due to the charge carrier trapping at Al dots in the active channel region.

Conventional organic static induction transistors (OSITs) have been directly fabricated on a source electrode formed on a substrate without the investigation of the effect of a surface treatment on device characteristics. We have fabricated the OSITs based on pentacene thin film with an ultrathin copper phthalocyanine (CuPc) layer. The influence of depositing this ultrathin CuPc layer on the source electrode on static characteristics was investigated. The obtained results provided an important fact indicating that a high on/off ratio of 230 and a high current of 3 µA in an organic SIT are achieved by the formation of a hole injection barrier that works as a tunneling layer on a source electrode. The barrier effectively controls the tunnel current from the source electrode by applying a gate voltage.

We propose a double heterojunction organic light-emitting diode (OLED) using a zinc oxide (ZnO) film, which works as a transparent and electron injection layer. The crystal structure of the ZnO films as a function of Ar/O2 flow ratio and the basic characteristics of the OLED depending on the ZnO sputtering conditions are investigated. Excellent characteristics of the novel OLED were obtained, as high as 470 cd/m2 at 22 V and 7.6 mA/cm2. The results obtained here demonstrate that the vertical organic light-emitting transistor (OLET) using a ZnO layer as an electron injection layer is promising as a key element for flexible sheet displays. © 2006 Wiley Periodicals, Inc. Electr Eng Jpn, 158(2): 49–55, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20151

We have fabricated the organic conductive wires and nano-transistors using co-evaporation method of tetrathiafulvalene (TTF) and tetracyanoquinodimethane (TCNQ) under AC electric field. Needle-like crystals of TTF-TCNQ charge transfer complex grow from an edge of gold electrodes along the electric field. The frequency dependence of the growth time of molecular wires indicates that AC electric field around 100 Hz is the most effective for making connected wires. Many connected wires were highly conductive which did not show any modulation of electrical conductivity with the gate voltage. However N-channel field effect transistor characteristics were observed with improvements of growth sequence. It is suggested that a tiny semiconductor area is formed at the connecting point of two conductive molecular wires.

Organic light emitting transistors which are vertically combined with the organic static induction transistor and organic light emitting diode are fabricated and the device characteristics depending on the structure of gate electrode are investigated. By optimizing the layer thickness and the size of slit-type Al gate electrode, high luminance modulation by low gate voltage as high as 1 V are obtained. The organic light emitting transistor described here is a suitable element for flexible sheet displays.

Organic static induction transistors (SITs) were fabricated with a Au(source)/organic/patterned-Al(gate)/organic/patternedAu(drain) structure employing a new concept, ‘spontaneous patterning of higher order structures’ (SPHOS). A selective mechanical exfoliation process was developed to replicate the pattern of gate electrode after a pre-patterned drain electrode. The I–V curve measured between the gate and the drain electrodes exhibited a good Schottky characteristic and the drain current of the SIT with higher order structure showed a clear modulation by the gate voltage.

Organic semiconductor transistors are expected for flexible displays, information tags, and the like. However, organic transistors have some disadvantages of current density and speed of operation, because of their high resistivity and low carrier mobility. To improve their performance, it is valuable to analyze the mechanism of operation. We have compared characteristics of lateral- and vertical-type transistors using pentacene evaporated films. The pentacene lateral-type FET characteristics showed large variation due to fabrication parameters such as deposition rate, substrate temperature, and film thickness. It was found that evaporated pentacene thin films have large grain gaps, which disturb carrier flow along the channel formed pentacene film/SiO2 interface direction and make FET characteristics unstable. It is assumed that pentacene films are not suitable lateral-type transistors. Accordingly, we have fabricated vertical-type organic static induction transistors (SITs) using pentacene evaporated films. The pentacene SITs show high-speed operation (cutoff frequency of 7.5 kHz) at relatively low voltages. Further optimization of SIT structure will improve the device performance. © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 149(2): 43–48, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.10500

The field-effect transistor (FET) characteristics of isolated copper phthalocyanine (CuPc) nano-crystals have been studied using AFM conductive probes as source electrodes.To extract the intrinsic carrier mobility of a single grain, the characteristics obtained were simulated by assuming a sub-exponential diode connected in series.The proposed model successfully reproduced most of the FET characteristics and the mobility was estimated to be 10 –10 cm yV s.On the other hand, characteristics with high y3 y 22 and low onyoff ratio were sequentially obtained using the same combination of CuPc grain and AFM probe.The characteristics of high onyoff ratio disagreed with the model near its off-state.The high on yoff ratio is explained by the dependence of the carrier injection rate on the gate voltage, which suppresses the off current. 2003 Elsevier Science B.V. All rights reserved.

We have fabricated organic light emitting transistors (OLET) combining static induction transistor with organic light emitting diode and investigated static and dynamic characteristics. The luminance of OLET is controlled by gate voltages as low as 1 V and excellent dynamic operation is obtained at 60 Hz. The results obtained here show that the OLET is a suitable element for flexible sheet displays.

We have fabricated tetrathiafulvalene-tetracyanoquinodimethane (TTF-TCNQ) molecular wires between a parallel cathode and anode (100 µm electrode gap) using the co-evaporation technique with an applied electric field. Wire-shaped microcrystals of TTF-TCNQ grew along the electric field. We have succeeded in fabricating connected wires with an optimum applied voltage. A narrow-gap (20 µm) electrode was used to grow wires with a low applied voltage, which make it possible to fabricate the connected wires easily. The measured I-V curve indicated Ohmic contact between the gold electrode and TTF-TCNQ. Semiconductor-like conduction of the fabricated TTF-TCNQ sample was shown by the temperature dependence of conductivity. Some of the co-evaporated TTF-TCNQ wires may tend to be semiconducting due to nonstoichiometry of TTF1-δ-TCNQ1.

Recent fabrication processes and characterizations of electronic devices using organic semiconductor films are described. In this chapter, we focus on the latest advances in organic transistor structures, in particular, the fabrication and characterization of functional thin organic semiconductor films. It is important to investigate the intrinsic electrical properties of organic semiconductor films, and the in situ optical and electrical measurements described here involve powerful techniques for the development of organic devices because a better understanding of the organic semiconductor growth mechanism and its basic electrical properties will not only enable better device performance but also lead to new functional physics. Other new functional devices, namely molecular nano-wire devices and metal-insulator transition devices, are described as well. Finally, the potential for the development of flexible organic electronic devices will be discussed.

Vertical type field effect transistors (FETs) are expected to be used for various organic devices because of their low-voltage, high-current and high-speed operation. We have fabricated lateral and vertical type FETs using copper-phthalocyanine evaporated films and measured the basic static and dynamic characteristics of these FETs. Although both transistors show field effect characteristics, the vertical type FET showed high-frequency and high-current characteristics under relatively low-voltage conditions as compared with those of lateral type FETs. These results demonstrate that the vertical FET operates as a static induction transistor and the short length between the source, drain and gate electrodes in the device structure improves the device characteristics.

We have fabricated field-effect transistors (FETs) using a TMTSF (donor) and TCNQ (acceptor) layered structure and investigated the basic FET characteristics. The transconductances of FETs depended on the substrate temperature.

Organic static induction transistors (SITs) for display devices are proposed and the basic electrical characteristics of the SITs are investigated. The organic SITs, using a copper phthalocyanine (CuPc) evaporated film as an active layer, have a layered structure of Au (drain)/CuPc/Al (gate)/CuPc/Au (source)/glass. The electrical characteristics show that the current flow from the source to drain electrodes is controlled by relatively low gate voltages. Furthermore, excellent characteristics such as a high current density of approximately 4 mA/cm2 and high-speed operation of less than 0.25 ms are realized by applying a buried Al grid electrode as the Schottky gate.

We have fabricated planar bottom-contact organic thin-film transistors as a function of the thickness of the pentacene active layer. The highest mobility of the planar bottom-contact transistors is 0.47 cm 2 /Vs with only a 7 nm pentacene active layer. Our planar bottom-contact transistors show much higher mobility than conventional bottom-contact counterparts and even higher than the reported mobility values of top-contact counterparts for each thickness in the range from 2.5 to 10 nm. We find that spike at the edges of source and drain electrodes seriously deteriorates device performance.

Static induction transistors (SITs) using copper phthalocyanine films and Al Schottky gate electrode are fabricated and the basic electrical characteristics are investigated. The electrical characteristics show that the current flows from the source to drain electrodes is controlled by the Al gate voltage and a typical SIT operation with non-saturating properties is examined. Furthermore, a high power and high frequency operation as organic transistors is obtained.

We have investigated the effect of an electric field on the molecular orientation of tetrathiafulvalene–tetracyanoquinodimethane (TTF–TCNQ) co-evaporated films, using an optical microscope, a scanning tunnelling microscope and X-ray diffraction. It is found that with an electric field applied TTF–TCNQ grows with the b-axis parallel to the electric field.

We fabricated field-effect transistors (FETs) using donor (TMTSF) and acceptor (TCNQ) stacked layers, and we investigated the change of conductivity in the charge transfer (CT) complex layer by applying gate voltages. Two types of FETs having TMTSF/TCNQ and TCNQ/TMTSF structures are examined. The stacked-layer FET shows a large transconductance compared with a single-layer FET. The experimental results demonstrate that the CT complex layer formed between donor and acceptor films mainly works as a conduction channel. Furthermore, the change in the degree of charge transfer (corresponding to conductivity change) is confirmed by infrared absorption spectra.

Langmuir-Blodgett (LB) films containing functional dyes were deposited directly onto optical fibers by the adsorption LB method. A merocyanine derivative having a long alkyl chain and rhodamine B were used as spreading and adsorbing molecules from the aqueous subphase, respectively. During the LB film deposition, absorption spectra from the optical interaction with the LB films at the core portion of the fiber were monitored using a multi-channel photo-detector system. Furthermore, the influence of the excitation light, which was guided into the fiber during the deposition, on the film deposition was investigated. The experimental results indicated that the in-situ optical measurement using optical fibers has high sensitivity and this is one of the promising methods to investigate the molecular interactions and the effect of the incident light on the LB film deposition.

Absorption spectra of adsorption Langmuir-Blodgett (LB) films were measured during and after the deposition of malachite green adsorbed merocyanine LB films on an optical fiber. The experimental results show that the in-situ optical monitoring using optical fibers is one of the powerful method to investigate the optical properties and the molecular interactions in the adsorption LB films.

TTF–TCNQ co-evaporated films were fabricated on variously surface–modified substrates and the structural investigation was carried out by scanning electron microscope and X-ray diffraction measurements. It was, indicated that the molecular orientation was controllable on a properly modified substrate by chosing an evaporation condition. Furthermore, the selective growth of the TTF–TCNQ film was achieved on the surface-modified substrate using a standard photolithographic technique.

A high-performance vertical-type organic transistor has been fabricated using bis(l,2,5-thiadiazolo)-p-quinobis(l,3-dithiole) (BTQBT) for the channel layer. The BTQBT molecules are oriented horizontally, with the molecular plane of each monolayer parallel to the substrate. The π–π stacking direction of the BTQBT molecules is aligned with the carrier transport direction in this vertical transistor. The modulated drain current density exceeded 1 A cm−2 upon the application of a gate voltage of less than 5 V. In addition, the device exhibits a high on/off current ratio of over 105.

We propose the hotpress method as a novel fabrication process of flexible sheet electronic devices. This process has the same advantages with the printing processes. And also, “solvent free” and “crystallization of organic semiconductor” are the additional advantages of this process. Sufficient crystallization of organic semiconductor contributes to the device performance, and no solvent emission provides a low environmental load process. Legal control on solvent emission will be overcome by this process. The low energy and no solvent emission process will also lead to not only the factory manufacturing but also the personal production of flexible sheet electronic devices in the future.

Field-effect transistors (FETs) using charge-transfer (CT)-complex Langmuir-Blodgett (LB) films were fabricated and their FET characteristics were measured. Four-layer (2 bilayers), 3-layer (a bilayer and a monolayer) and monolayer of Y-type TMPD-CnTCNQ LB films were examined as active layers of the FET. The FET characteristics strongly depended on the number of CT-complex layers. The monolayer FET showed the highest dependence of drain-source current (IDS) on gate voltage (VG) although the film was the least conductive among the three. Elimination of bilayer units, of which the structure is symmetric against the substrate normal, was concluded to be essential for improving the VG dependence. The cutoff frequency of the CT-complex FET was estimated to be 5 Hz.

An optical fiber sensor for albumin detection has been fabricated and tested. The adsorption Langmuir–Blodgett (LB) method was employed to form organic thin films on the optical fiber. The spectral change can be monitored by the interaction between the evanescent light from the fiber core and the adsorption LB films. A relatively high sensitivity and linear relationship between the spectral change and the albumin concentration were obtained.

PROBLEM TO BE SOLVED: To provide a vertical type organic transistor at a low cost wherein high operational speed and high power are realized and mass production is enabled with superior reproducibility. SOLUTION: In the vertical type organic transistor wherein a source electrode 2, a first organic semiconductor layer 3, a gate electrode 4 of a comb type or a mesh type, a second organic semiconductor layer 5, and a drain electrode 6 are formed in order, the first organic semiconductor layer 3 and the second organic semiconductor layer 5 are constituted by using different organic semiconductor material, so as to form a potential barrier on an interface of the first layer 3 and the second layer 5. The potential barrier is generated by potential energy difference of the organic semiconductor material. For example, the potential barrier can be formed by constituting the first layer 3 and the second layer 5 of the same conductivity type organic semiconductor material, or can be formed by constituting the layers 3, 5 of different conductivity type organic semiconductor material. COPYRIGHT: (C)2004,JPO