The HfOxNy films grown at 300degreesC in plasma and N-2 ambient using hafnium tertiary-butoxide (Hf[OC(CH3)(3)](4)) as the precursor in the absence of O-2 were prepared to improve the thermal stability of HfO2-based gate dielectrics. The HfOxNy films showed a 200degreesC higher crystallization temperature and more suppression in the growth of an interfacial layer than that of HfO2 films when films were annealed at 700degreesC in a nitrogen ambient. The HfOxNy films showed an improvement of interface charge trap densities by a forming gas annealing treatment, resulting in much more improvement in drive current and subthreshold swing (S.S.) than those of HfO2 films. (C) 2004 American Vacuum Society.