We report on the fabrication of pentacene thin-film transistors (TFTs) with a poly-4-vinylphenol (PVP)/yttrium oxide (YOx)/PVP triple-layer dielectric deposited on an indium-tin oxide (ITO)/plastic substrate. Our PVP/YOx/PVP triple layer exhibited 2 orders of magnitude lower gate current leakage than that of a PVP/YOx double layer because the former has a PVP buffer to cope with the irregular surfaces of the ITO/plastic substrate. Adopting the triple-layer dielectric, our pentacene TFTs with NiOx and Au source/drain electrodes exhibited high field mobilities of similar to 1.37 and 0.84 cm(2)/V s, respectively, under low driving voltage conditions (less than -8 V). We conclude that our triple-layer approach is quite a promising and practical way to realize a flexible low-voltage high-performance organic TFT on ITO/plastic substrates with rough surfaces. (c) 2007 The Electrochemical Society.