The high quality silicon oxide films were prepared by plasma-enhanced chemical vapor deposition (PECVD) using tetraethylorthosilicate (TEOS)-oxygen based chemistry. The O2- or N2O-plasma treatments were performed on the as-deposited films as an attempt to improve the properties of the TEOS oxide films. TEOS oxide film deposited at lower pressure had lower Si–OH content, less carbon impurity, and flatter surface, and hence had better electrical properties. Both O2- and N2O-plasma would decrease the oxygen content of the oxide film, which led the composition of the film to deviate from the stoichiometric SiO2. The O2-plasma treatment did not show the encouraging effect on the chemical structure and electrical properties of the TEOS oxide films. In contrast, the N2O-plasma treatment could be a promising means to improve the breakdown field and leakage current density of the TEOS oxide films, which was accomplished by the N2O-plasma effect to facilitate the passivation of dangling bonds, linking reaction of Si–OH bonds, nitridation reaction and densification of the amorphous silicon oxide network.