Films of silicon dioxide and silicon oxynitride were grown by LPCVD using gas-phase mixtures of Si2Cl6, N2O, and NH3 in the temperature range 550°–850°C. The activation energy for SiO2 deposition was 29 kcal/mole. Under comparable pressure and temperature conditions, growth rates of SiO2 from Si2Cl6 were at least three times higher than those obtained using SiH2Cl2 or SiH4. The effect of temperature and reactant flow ratios on film composition, stress, refractive index, etch rate, and uniformity were studied, and these properties were found to be comparable to those in films deposited from SiH2Cl2 and SiH4. The effect of N2O/NH3 ratio on physical properties was investigated for oxynitride films. The dependence of these properties on film composition was the same regardless of the CVD reactant mixture used. However, the NH3 to oxidant ratio required to obtain a specific film composition was strongly influenced by the oxidant and silicon precursor used. Comparisons are made to the LPCVD systems: SiH2Cl2-N2O-NH3, SiH4-NO-NH3, and SiH4-CO2-NH3. © 1989, The Electrochemical Society, Inc. All rights reserved.