The structural properties of silicon oxynitride films grown in a N2O environment at temperatures higher than 900 C and for use as gate dielectrics in vertically diffused power metal oxide semiconductor field effect transistor (PowerVDMOS) technologies have been studied by means of X-ray photoelectron spectroscopy. The progressive modifications of the bonding environments upon reaching the oxynitride-silicon interface have been analyzed as well as of the relation between these modifications and the selected oxynitridation process. The results show that the chemistry of the oxynitride layer is a rather complex one, and it significantly and progressively changes by moving toward the silicon interface, in a way strongly affected by the growth process. In particular, the medium thermal budget processes (950 degrees C, 20-60 min) favor the formation of a relatively uniform distribution of the single oxidized O-N-Si-2 bonds both at the interface and throughout its immediate backstage. Such findings can help in assessing the role played by the nitridation process in the quality and reliability performances of the final device. (c) 2007 The Electrochemical Society.