In this study, a high breakdown voltage (V-BR) enhancement-mode (E-mode) MgxZn1-xO channel thin-film transistor (TFT) was realized using a gadolinium oxide (Gd2O3) gate insulator and CF4 plasma treatment technologies. The threshold voltage (V-T) for conventional Gd2O3/MgxZn1-xO TFTs was -2.8 V and this value was adjusted to + 0.1V after nine minutes of CF4 plasma treatment beneath the gate regime. X-ray photoelectron spectroscopy (XPS) results indicated that the fluorine atoms reduced the number of oxygen vacancies in MgxZn1-xO channel, resulting in an extreme low carrier concentration beneath the gate region. Additionally, this E-mode TFT had favorable surface roughness and low interface state density. (C) 2011 The Electrochemical Society. [DOI: 10.1149/ 2.004202esl] All rights reserved.