Top-contact pentacene TFTs were successfully scaled down from 20 μm to 1.8 μm for the channel length (L_C) by using silicon nitride membrane shadow mask. When LC was reduced to 1.8 μm, pentacene TFTs with the grain size of a few micrometer showed poor on/off current ratio (I_on/I_off) of 10³ and high mobility of 0.25 cm²/Vsec, whereas pentacene TFTs with the grain size of sub-micrometer resulted in low mobility of 0.08 cm²/Vsec, but good I_on/I_off of 5.7×10⁶. To obtain both high mobility and good I_on/I_off for the scaled-down OTFTs at the same time, two-step-deposition (TSD) technique was proposed and resulted in I_on/I_off of 10⁷ as well as mobility of 0.19 cm²/Vsec even for the TFT with L_C of 1.8 μm. To our best knowledge, this result is one of the best electrical characteristics among the reported electrical performance of OTFTs scaled down to L_C of 1.8 μm.