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A novel integratable metal–oxide–semiconductor field-effect transistor (MOSFET) with a trench source (TS) and a trench gate (TG) (TS–TG MOSFET) is proposed. The TS and TG cause a strong assistant depletion effect and thus dramatically increase the N-drift doping concentration (N d). Moreover, an accumulation layer beside the TG is formed and offers a continuous low-resistance path in the on-state. Therefore, the novel MOSFET effectively reduces specific on-resistance (R on,sp). The TS–TG MOSFET not only has the merits of low R on,sp and the easy parallel connection of vertical double-diffused MOS, but also possesses the advantage of ease of integration like the LDMOS. The breakdown voltage (BV) of 61 V and the R on,sp of 0.133 mΩ cm2 are obtained for the TS–TG MOSFET, with a significant optimised trade-off between R on,sp and BV.

A novel process technique for fabricating trench gate DMOSFETs using the two-step trench technique and trench contact structure is realised to obtain higher cell density and lower on-resistance. Using this process technique, a remarkably increased trench gate DMOSFET with a cell pitch of 1.6 µm and a channel density of 130 Mcell/in2 are obtained. The fabricated device has a low specific on-resistance of 0.28 mΩ · cm2 with a blocking voltage of 43 V, which is about 23 % lower than that of the device fabricated by the previous method.

A new and simplified process for fabricating a high density n-channel trench gate power MOSFET using four mask layers and a sidewall spacer technique is proposed. Use of this process has enabled a remarkably increased high density (100 Mcell/in/sup 2/) trench MOSFET with a cell pitch of 2.5 /spl mu/m to be realised. Furthermore, the p-base, n-source, and trench gate regions were formed by the same mask layer, which made it possible to reduce the number of processing steps. The fabricated device had a low specific on-resistance of 0.7 m/spl Omega/cm/sup 2/ with a breakdown voltage of 46 V.

An ultralow specific on-resistance power UMOSFET structure with the trench-gate extending down to the N+ substrate is presented. Specific on-resistances in the range 100–200 μΩ cm2 have been experimentally demonstrated for devices capable of supporting up to 25 V. Comparison of theoretical and experimental results is provided.