HfOxNy films were prepared using hafnium tertiary-butoxide {Hf[OC(CH3)(3)](4)} in a plasma and N-2 ambient to improve the thermal stability of hafnium-based gate dielectrics. The incorporation of 10% nitrogen into HfO2 films resulted in a smooth surface morphology and a crystallization temperature as high as 200degreesC compared with pure HfO2 films. TaN/HfOxNy/Si capacitors showed stable capacitance-voltage characteristics even at a postmetal annealing (PMA) temperature of 1000degreesC in a N-2 ambient and a constant value of 1.6 nm equivalent oxide thickness irrespective of an increase in the postdeposition annealing (PDA) and PMA temperatures. The leakage current densities of HfOxNy capacitors annealed at PDA and PMA temperatures of 800 and 900degreesC, respectively, were approximately one order of magnitude lower than that of HfO2 capacitors. (C) 2004 The Electrochemical Society.