SiO2 films have been deposited using TEOS and oxygen in a microwave excited plasma reactor at a pressure of 3 mTorr. Layers have been characterized using FTIR, refractive index, chemical etch rate, electron spin resonance, Rutherford backscattering spectroscopy, nuclear reaction analysis and electrical measurements. The influence of substrate temperature and impinging ion energy has been studied. Layers having satisfactory physical properties were obtained for deposition at 400-degrees-C with a substrate polarization of the order of - 120 V.