In this work, we develop methods for fabricating high quality dielectric films for nonvolatile memory applications. Oxide/Si-rich nitride/oxide structures are fabricated where the Si-rich nitride layer was deposited by the low pressure chemical vapor deposition (LPCVD) technique. With a Si-rich nitride layer, the Fowler-Nordheim tunneling voltage can be cut down to 3 V for oxide thickness of about 100 Angstrom. By reoxidizing the Si-rich nitride layer, secondary ion mass spectroscopy study reveals that the hydrogen content of nitride film and its interface can be reduced by more than 40%. With this method, high nitrogen content oxynitride and smoother oxynitride/oxide interfaces result and the interface charge trapping can be improved remarkably.