This study reports the enhanced electrical properties of InGaZnO4 thin film transistors (TFTs) with sputter-deposited poly(methyl methacrylate) (PMMA)/Ba0.6Sr0.4TiO3 (BST) stacked gate dielectrics. A noticeable reduction in the leakage current density (similar to 10(-8) A/cm(2) at 0.3 MV) was achieved by coating a PMMA overlayer. The InGaZnO4 TFTs utilizing the PMMA (30 nm)/BST (270 nm) stacked gate dielectrics exhibited a high on/off current ratio of 2.6 X 10(6), a high field effect mobility of 10.2 cm(2)/V center dot s, and a low threshold voltage of 1.1 V. Using stacked gate dielectric layers, we realized the low voltage operating InGaZnO4 TFTs on a poly(ethylene terephthalate) substrate. (C) 2010 The Electrochemical Society. [DOI: 10.1149/1.3479689] All rights reserved.