In this work, depletion-mode magnesium doped zinc-oxide (MgZnO) channel thin film transistors (TFTs) with zirconium oxide (ZrO2) gate insulator were fabricated using radio frequency magnetron sputtering deposition. Sputtered MgZnO TFT channel layer performed an average transmittance of 90% and an improved energy bandgap of 5.02 eV after 700 degrees C post annealing. X-ray photoelectron spectroscopy (XPS) results indicated that the binding energy of Zn-O bonds and Mg-O bonds were enhanced following with the increasing of the post annealing temperatures. The low frequency noise spectra also indicated that the ZrO2/MgZnO was dominated by flicker noise and gate leakage induced noise was suppressed. (C) 2011 The Electrochemical Society. [DOI: 10.1149/1.3606545] All rights reserved.