This study examines bilayer source-drain electrodes for organic thin-film transistors (OTFTs). Between the pentacene layer and the Au layer, a p-type metal oxide layer was inserted. p-Type metal oxide was prepared by thermally evaporating copper oxide (CuO). To compare the effect of the CuO layer, a device with a single Au layer as the source-drain electrode was fabricated. The field-effect mobility of the device with the CuO (10nm)/Au (50 nm) bilayer electrodes was 0.34 (+/-0.04) cm(2)/V s, and it was higher than the device with a single Au layer electrode [0.16 (+/- 0.03) cm(2)/V s]. (c) 2007 The Electrochemical Society.