In this work, we report studies on the Si, N and O local bonding in silicon oxynitride films deposited by PECVD technique, with chemical compositions varying from SiO2 to Si3N4, utilizing N2O + N2 + SiH4 and N2O + NH3 + SiH4 as precursor gaseous. The films are characterized by X-ray absorption near edge structure (XANES) at the Si-K, N-K and O-K edges, in order to determine the local structure and by Rutherford backscattering (RBS) spectroscopy to obtain their chemical composition. The results at the Si-K edge show, for the samples with lower nitrogen content, a homogeneous structure compatible with a random distribution of Si-N and Si-O bonds (random bonding model) and for the samples with higher nitrogen incorporation a structure composed by two phases compatible with the random mixture model (RMM). On the other hand, the analysis of the results at the N-K edge demonstrates two features, which are attributed to two different nitrogen sites, a trigonal Si3N4-like site and SiO2-like sites, corresponding to nitrogen substituting O in Si-O-Si bridges, which originate a resonant line (RL) in the XANES spectra at approximately 399.1 eV. Finally, the results at the O-K edge show only one edge, attributed to O-Si bonds, independently of the N and O concentration, for both gaseous mixtures. © 2006 Elsevier B.V. All rights reserved.