This letter describes a process for the preparation of high-quality tantalum oxynitride (TaOxNy) via NH3 annealing of Ta2O5, for use in gate dielectric applications. Compared with tantalum oxide (Ta2O5), a significant improvement in the dielectric constant was obtained by the NH3 treatment. In addition, light reoxidation in a wet ambient at 450 °C resulted in a significantly reduced leakage current. We confirmed nitrogen incorporation in the tantalum oxynitride (TaOxNy) by Auger electron spectroscopy. By optimizing the nitridation and reoxidation processes, we obtained an equivalent oxide thickness as thin as 1.6 nm and a leakage current of less than 10 mA/cm2 at -1.5 V. © 2000 American Institute of Physics.