The electrical and optical properties of amorphous indium gallium zinc oxide (a-IGZO) films, which can be used as a channel layer, deposited by radio frequency (rf) magnetron sputtering system at room temperature (RT), were investigated as function of various gas flows. The optical transmittance of films deposited under At, O-2 / Ar + O-2 and O-2 / Ar-4% H-2 + O-2 atmospheres in the visible wavelength was consistently above 90% at a wavelength of 550 nm at all gas flows, although the film deposited under Ar-4% H-2 atmosphere exhibited a transmittance of below 50%. The carrier concentration and mobility of the a-IGZO films fabricated under At and Ar-4% H-2 were observed slight decrease as a function of the flow, respectively. The thin film transistors (TFrs) with an a-IGZO channel deposited under At and Ar-4% H-2 atmosphere exhibited the following good characteristics: Vth of 0.34 V, mu(FE) of 3.6 cm(2) V-1 s(-1), on/off ratio of 10(6), and S value of 0.04 V decade(-1). (C) 2009 Elsevier B.V. All rights reserved.