A 5 angstrom thick tantalum nitride (TaNx) interface layer was inserted between an 8 nm Zr-doped tantalum oxide (TaOx) high-k film and a silicon substrate to improve dielectric properties for metal-oxide-semiconductor (MOS) gate dielectric applications. Compared to the Zr-doped TaOx film without the TaNx interface, the stacked structure showed improvement in the dielectric constant, leakage current density, and dielectric breakdown strength. However, the flatband voltage shift and interface state densities were slightly degraded. Hysteresis of C-V curves did not change substantially with this TaNx insertion. Structural and chemical analyses, i.e., secondary ion mass spectroscopy (SIMS) and X-ray photoelectron spectroscopy (XPS), were done to investigate this TaNx interface layer. The results suggested that TaNx reacted with oxygen atoms from the high-k film and formed tantalum oxynitride (TaOxNy) after being annealed at 700 degrees C in O-2, which may be responsible for the observed improvement on dielectric properties. (c) 2005 The Electrochemical Society. All rights reserved.