The as-deposited WO3 thin films were post-annealed at different temperatures (300 degrees C and 600 degrees C) in air to investigate a correlation between crystallinity and switching behavior of WO3 thin films. Associating the results of XRD, FTIR, XPS and FESEM measurements, the annealing-caused crystallinity change contributes to the variation of the switching behaviors of the WO3 thin films. The as-deposited WO3 films with low crystalline structure are preferred for random Ag conducting path, resulting in large switching ratio but fluctuating I-V hysteresis, whereas the annealed WO3 films with crystallized compact structure limits Ag conducting path, favoring the stable I-V hysteresis but small switching ratio. It is therefore concluded that electrochemical redox reaction-controlled resistance switching depends not only on electrode materials (inert and reactive electrodes) but also on crystallinity of host oxide. (C) 2014 Elsevier B.V. All rights reserved.