Abstract A compositional study of silicon rich oide (SRO) films obtained by low pressure chemical vapor deposition (LPCVD) an plasma enhanced chemical vapor deposition (PECVD) is presented. As deposited and annealed SRO films were characterized by mean Infrared (IR) and x-ray photoelectron spectroscopy (XPS) techniques. IR spectra from SRO obtained bye PECVD showed absorption bans related to silicon-hydogen bands due to Si-O motion were observed. Moreover, XPS analysis demonstrated that SRO-PECVD films contain a higher nitrogen concentration that the LPCVD ones. All the SRO films were subjected to thermal annealing in order to investigate the changes in the composition of the films. The hydrogen and nitrogen have shown being an important parameter to infuence the optical properties of these films.