We find that an incorporation of the small amount of Si in the ZnSnO stabilizes the device performance significantly. Through the first-principle calculation, we find that the formation of O-deficient states is easily suppressed by Si-doping due to the volume shrinkage effect, which leads to the stable device operation. This behavior is consistent with the X-ray photoelectron spectroscopy measured data. (C) 2013 Elsevier B. V. All rights reserved.