HfO@sub 2@ is a leading candidate for replacement of SiO@sub 2@ in CMOS field effect transistors. Past work has shown this material has a tendency to interdiffuse and react with the substrate forming a less-than-ideal abrupt interface. In this paper, HfO@sub 2@ thin film stability results for a remote plasma nitrification process is reported in which the Si substrate is exposed to a N@sub 2@/He plasma then annealed in vacuum before the gate oxide deposition process. The nitrided surface and subsequently deposited films were studied using ellipsometry and x-ray photoelectron spectroscopy before and after annealing treatments. This method is compared to other procedures for the addition of nitrogen developed in our laboratory including the plasma enhanced deposition of HfO@sub 2@ using N@sub 2@O and N@sub 2@ plasmas, and post deposition treatment of the films with a remote N@sub 2@ plasma. Nitrogen plasma treated substrates showed a nitride layer approximately 16 @Ao@ thick which was sufficient to prevent significant film/substrate interdiffusion and thickness growth for 2 min., 800@degree@C anneals in Ar.