Inorganic-solid-state electrolyte tantalum oxide thin films were deposited by reactive DC magnetron sputtering to improve the leakage and deterioration of traditional liquid electrolytes in electrochromic devices. O(2) at 1-20 sccm flow rates was used to deposit the tantalum oxide films with various compositions and microstructures. The results indicate that the tantalum oxide thin films were amorphous, near-stoichiometric, porous with a loose fibrous structure, and highly transparent. The maximum charge capacity was obtained at an oxygen flow rate of 3 sccm and 50 W. The transmission change of the Ta(2)O(5) film deposited on a WO(3)/ITO/glass substrate between colored and bleached states at a wavelength of 550 nm was 56.7%. The all-solid-state electrochromic device was fabricated as a multilayer structure of glass/ITO/WO(3)/Ta(2)O(5)/NiOx/ITO/glass. The optical transmittance difference of the device increased with increasing applied voltage. The maximum change was 66.5% at an applied voltage of +/- 5 V. (C) 2011 Elsevier B.V. All rights reserved.