This study investigates the elimination of oxygen vacancy and nitrogen gap in hafnium oxide films induced by different nitridation process. Based on previous studies, the oxygen vacancy in hafnium oxide could be passivated by the diffusion nitrogen, thus, enhancing the performance and reliability of n-MOSFET. On the other hand, as for p-MOSFET device, the nitrogen diffuses into the channel interface to generate interface defects, causing S.S. degradation to the device. However, in the HfO₂ thin film, the nitrogen interstitial defect will be generated when the concentration of nitrogen is higher. These interstitial defects are located in HfO₂ with the energy level below the mid-gap. Therefore, the holes can be trapped into the nitrogen interstitial defects while they transport from the channel to the gate. This work investigates the reduction of nitridation time and annealing time to device to further verify the hafnium oxide layer of nitrogen and oxygen vacancies bonding to reduce nitrogen interface defects. The influence of different nitrogen concentration and annealing time to device performance and reliability are also investigated.