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CH3NH3PbI3 perovskite films with full coverage and negligible roughness have been obtained by the two-step sequential thermal evaporation (TSSTE) process, which are further applied to fabricate thin-film transistors (TFTs). To gain the optimal electrical characteristics in our TFTs, the effect of the evaporation amount of PbI2 on the crystallization and thickness of CH3NH3PbI3 films is studied during the process of TSSTE. As a result, we demonstrate a thin-film field-effect transistors possessing a hole field-effect mobility of 3.55 cm2 V− 1 s− 1 as well as on/off ratio greater than 105 with the optimal CH3NH3PbI3 films as the channel layer. Through a further comparative analysis, MoO3 buffer layer is inserted between the perovskite channel layer and the source-drain electrode to improve the contact resistance of TFTs. As an understanding of device mechanism, a fact that insertion of MoO3 buffer layer into the Au/perovskite interface significantly reduced the contact resistance from 705 to 0.2 kΩ cm is unveiled. By inserting MoO3 buffer layer, the hole field-effect mobility of the CH3NH3PbI3 organic-inorganic hybrid TFTs can reach to 7.47 cm2 V− 1 s− 1. [ABSTRACT FROM AUTHOR]