A stable aluminum oxide (Al2O3) film was obtained on a plastic substrate for use as low-temperature polycrystalline silicon (LTPS) thin film transistors (TFT) in a flexible display by in situ plasma oxidation prior to the deposition of gate dielectric grown by plasma enhanced atomic layer deposition (PEALD). The hysteresis value was minimized to about 2 V when more than 100 W of plasma power was applied during oxidation, which provides a formation of a high quality interfacial oxide layer. Moreover, by post-annealing at 200 degrees C without a plasma application, flat band voltage was shifted to near 1.2 V, which may be attributed to defect passivation by H diffusing out from SiNx:H. (C) 2009 Elsevier Ltd. All rights reserved.