Lanthanum oxide thin films were deposited using alternate injections of La(iPrCp)(3) and H2O at various substrate temperatures. The leakage current density increased with decreasing substrate temperature, although the films showed similar equivalent oxide thickness (EOT). The proper substrate temperature, at which La2O3 thin films with a low EOT and low leakage current were deposited, was 300 degrees C. During post-deposition annealing (PDA) in an N-2 atmosphere, a remarkable amount of Si diffusion occurred. However, annealing in an NH3 atmosphere improved the thermal stability and dielectric constant of the La2O3 thin films, due to the incorporation of nitrogen. The typical EOT and leakage current of the La2O3 thin films, annealed in NH3 at 800 degrees C, were 2.2 nm and 1.7 x 10(-8) A/cm(2) at - 1 V, respectively. The amount of Si atoms which diffused into the La2O3 films decreased in the sequence: O-2-annealed, NH3-annealed, and pre-nitrided samples. A pre-nitridation step to form an SiNx reaction barrier was effective at increasing the thermal stability. (c) 2007 The Electrochemical Society.