The incorporation of nitrogen in HfO2 gate dielectrics has been reported to be beneficial for electrical performance. The improvement in the electrical characteristics of HfO2 thin film with plasma nitridation process or plasma fluorination process has also been examined. In this study, dual plasma, CF4 pre-treatment and nitrogen post-treatment, treatments were performed on HfO2 MIS capacitor for further improvement on reliability characteristic. We examine the reliability properties and the current conduction mechanism of HfO2 thin films. The frequency dispersion and constant voltage stress (CVS) characteristics of the samples were analyzed to estimate the improvement. According to the present study, dual plasma treatment could be better than single plasma treatment and would be an effective approach for HfO2 dielectric improvement.