Post deposition annealing is a critical process for the quality improvement of gate oxides on III-V MOS capacitors. Though high temperature annealing would effectively repair defects, it could also induce undesired electrical characteristics due to the crystallization of the gate oxide. In this work, we investigate the novel two steps annealing technique to improve the HfO 2/In0.7Ga0.3As MOSCAP properties. The two steps process takes advantage of 1st high temperature annealing (550°C) to improve the interface quality and 2nd low temperature annealing (450°C) for curing bulk oxide without oxide crystallization. The two steps annealing technique greatly improves the HfO2/In 0.7Ga0.3As properties as compared to single step process and is expected to be helpful for future III-V MOSFET development.