Metallorganic chemical vapor deposition (MOCVD) hafnium (Hf)-silicate gate dielectrics were treated by plasma nitridation in an Ar/N-2 ambient. The nitridation concentration in MOCVD Hf-silicate gate dielectrics can be controlled by altering the pressure during plasma nitridation; nitrogen is mainly distributed near the surface of the high-k films. The effective oxide thickness decreased with nitrided treatment due to suppression of the growth of the interfacial oxide, and a value of 1.5 nm was obtained using nitrided Hf-silicate (HfSiON) gate dielectrics. The gate leakage currents for HfSiON gate dielectrics were reduced by more than four orders of magnitude compared to reference SiO2 films. The effective mobility curves for HfSiON gate dielectrics were almost the same as the reference 1.6 nm SiON films at 0.8 MV/cm. (c) 2005 The Electrochemical Society.