Thin silicon oxynitride films were deposited on Si(100) substrates using nitrogen plasma at various exposure times, followed by thermal oxidation in dry O-2 without the use of toxic or global warming gases. Secondary ion mass spectroscopy measurements confirmed that nitrogen is confined to the immediate vicinity of the surface. The damage induced in the thin silicon oxynitride film after exposure to nitrogen plasma for between 10 and 60 s was estimated from an analysis of capacitance-voltage and current-voltage measurements. Generation of different densities of positive oxide charge was observed. Correlation between the local bonding structures in the oxynitride films and the electrically active defective states at the oxynitride/Si interface are also discussed. It is proposed that improved electrical characteristics such as positive charge trapping, interface state density, leakage current, and stress immunity of thin silicon oxynitride films, can be obtained by using an optimal plasma exposure time of approximately 30 s. The preliminary results obtained in this study indicate that these oxynitride films can be considered as potential candidates for ultra-thin gate oxide flash memory applications.