In this study, a simple method of fabricating a thin-film transistor (TFT) with a double-layered channel using indium-zinc-oxide (IZO) films was proposed. Two IZO films used as channel layers were consecutively deposited via sputtering without stopping the vacuum and only by changing the volumetric fraction of the additive O(2) gas during the deposition. Time-of-flight secondary ion mass spectrometry (ToF-SIMS) analysis showed a large difference in the depth profiles of the InO(-) and InO(2)(-) ions between the two IZO layers. Compared to the conventional single-IZO-channel TFT, the double-IZO-channel TFT that was fabricated using the proposed two-step deposition method showed greatly improved electrical characteristics: the on/off-state current ratio was increased from 1.30x10(5) to 1.03x10(6), and the field effect mobility was enhanced from 1.2 to 9.3 cm(2)/Vs. Crown Copyright (C) 2011 Published by Elsevier B.V. All rights reserved.