High-k dielectric such as Hf-based dielectric has been considered to be inevitable for 45-nm CMOSFET technology node. The incorporation of Al in Hf-based dielectrics has been proven as a solution to the problem about thermal stability. Moreover, there have been some researches which describe that the reliability of the high-k dielectrics could be improved by the nitridation process. In this study, we examine the effect of different inductively coupled plasma (ICP) nitridation processes on the reliability of HfAlOx thin films. The hysteresis, stress induced leakage current (SILC) and constant voltage stress (CVS) characteristics of the nitrided HfAlOx thin films were preformed to prove the improvement effect of the plasma nitridation. Based on our experimental results, the ICP nitridation process would be an effective technology to improve the reliability of HfAlOx thin films.