We have proposed an approach to grow ultra-thin oxynitride film with high nitrogen concentration (≈13 at%) on the top and low interface state density (Dit=2×1010 cm-2 eV-1). In general, a high-nitrogen oxynitride film provides a rather reliable and higher dielectric constant. In this method, oxynitride growth included three process stages-chemical oxide growth, nitridation and subsequent dry oxidation. By this technique, the films demonstrate the desirable nitrogen concentration profile and excellent properties in terms of low Dit, low leakage current, and high endurance in stressing. Better controllability in film thickness may be achieved because the oxidation rate of the nitride-chemical oxide is much smaller than that of the conventional oxide. Most importantly, this process is simple and fully compatible with current process technology.