Plasma enhanced chemical vapor deposition (PECVD) of nitrogen-incorporated silicon oxide thin films using TMOS (tetramethoxysilane) and N2O plasma is studied. The effects of the TMOS and N2O pressure ratio on the properties of the film and the plasma are investigated. The intensities of light emission from molecules and radicals in the plasma are measured by optical emission spectroscopy (OES). The deposited films are analyzed by in-situ ellipsometty, and Fourier transform infrared spectroscopy (FTIR). The optical properties are measured by photoluminescence (PL). As the partial pressure of N2O decreases, the refractive index begins to decrease, reaches a minimum, and then increases again. When the oxygen content in the plasma phase reaches a maximum, the refractive index reaches a minimum. We attribute the decrease of the refiractive index to the incorporation of more oxygen. The FTIR absorption band from about 850 to 1000 cm(-1), which call be attributed to the formation of SiON is observed. A broad PL appears around 1.9-2.4 eV As the oxygen content increases, the PL spectrum shifts toward a higher energy. (c) 2005 Elsevier B.V. All rights reserved.