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The effects of Ti incorporation in La₂O₃ gate dielectric on the electrical characteristics of amorphous InGaZnO thin-film transistor are studied. Compared to the control sample with La₂O₃ gate dielectric, the device performance can be significantly improved with an appropriate Ti dose. Accordingly, the sample with a Ti/(Ti&#x002B;La) ratio of 6.7&#x0025; presents a high saturation mobility of 28.1 cm²V^&#x2212;1s^&#x2212;1, small subthreshold slope of 0.17 V/dec, large on/off current ratio of <inline-formula> <tex-math notation="LaTeX">$7.2\times 10$ </tex-math></inline-formula>⁷, and acceptable hysteresis. We attribute such an improvement to the passivation of the defect states at/near the La₂O₃/InGaZnO interface as well as the enhancement of moisture resistance of La₂O₃ film due to Ti incorporation. However, excessive Ti incorporation leads to device degradation, which is due to more oxygen vacancies generated in gate dielectric.