[en] The impact of thermal treatment temperature on the density of oxygen-related defects in the lattice of amorphous InGaZnO is investigated. X-ray photoelectron spectroscopy results state that the oxygen-deficient defects are remarkably reduced and the quality of a-IGZO film is effectively improved after annealing under the appropriate temperature of 350 °C. With the help of synergistic effect of proper treatment temperature and high quality IGZO layer, the IGZO thin-film transistor exhibits outstanding electrical properties, including a field effect mobility of 8.70 cm² V⁻¹ s⁻¹, a threshold voltage of 1.81 V, a subthreshold swing of 307 mV/dec., and a small hysteresis of 0.32 V. Moreover, the transmission line model clarifies that the suitable heating temperature is beneficial to alleviate the source/drain contact resistance as well as the effective channel length loss. More notably, the positive bias stress stability of a-IGZO TFTs is simultaneously improved. (paper)