We fabricated thin film transistors (TFTs) using HfInZnO thin films as active channel layers. The thin films of HfInZnO were deposited by co-sputtering from HfO2 and InZnO targets. The HfInZnO TFTs were investigated according to the radio-frequency power applied to the HfO2 target. The transistor on and off currents were greatly influenced by the composition of Hf atoms suppressing the formation of oxygen vacancies. The electrical characteristics of the TFTs show a field-effect mobility of 3.53 cm(2) V-1 s(-1), a threshold voltage of 1.28 V, an on/off ratio of 1.4x10(-7), and a subthreshold swing of 95 mV/dec. (C) 2010 The Electrochemical Society. [DOI: 10.1149/1.3428510] All rights reserved.