High-k Ti1-xSixO2 gate dielectric layers were prepared at room temperature by RF magnetron sputtering using SiO2 and TiO2 targets to investigate their applicability to transparent thin-film transistors as well as metal-oxide-semiconductor field-effect transistors. Based on XRD and XPS analyses, it was found that, regardless of the deposition time, the Ti1-xSixO2 gate dielectric layers had more stable Si-based phases with stronger Si-O bonds with increasing SiO2 RF power. As SiO2 RF power increased, the capacitance of the dielectric layers decreased due to the higher fraction of the Si-based phases, and the leakage current decreased, dominantly because of the decrease in oxygen vacancies due to the formation of stoichiometric SiO2. The Ti1-xSixO2 gate dielectric layers exhibited high transparency above 80% and moderate bandgap of 4.1-4.2 eV, which can be applied to transparent thin-film transistors. (C) 2007 Elsevier B.V. All rights reserved.