Pentacene organic thin-film transistors (OTFTs) having acrylic polymer gate dielectric were fabricated with the change of UV/ozone treatment on the surface of gate dielectric. As UV/ozone exposure time increased, threshold voltage was shifted towards positive values from -0.7 V to 6.2 V and saturation mobility was dramatically increased from 0.07 cm(2)/Vs to 2.66 CM2/Vs while the amount of hysteresis was enlarged. The increase of hysteresis and the non-saturation behavior of output characteristics were attributed to the generation of hydroxyl groups through polymer dissociation during UV/ozone treatment because the hydroxyl groups making the surface of polymer gate dielectric more polar played as electron traps. (C) 2009 Elsevier Ltd. All rights reserved.