Ozone/TEOS thermal chemical vapor deposition (CVD) has been investigated for SiO2 deposition bn Si, using a cold-wall research reactor equipped to determine the effects of precursor concentration, deposition temperature (300-500 degrees C), and pressure (30-200 Torr) on deposition rates, etch rates, and step coverage in the regime of subatmospheric CVD (SACVD). Deposition rates first increase with substrate temperature then reach a maximum and finally decrease distinctly at higher temperatures, with the latter reflective of reactant depletion in the gas phase. Wet etch rates decrease at higher deposition temperature and higher ozone/TEOS ratio, indicating improved film quality under these conditions. Elevated deposition temperatures significantly improves step coverage in high-aspect-ratio trenches, but decreases deposition rates. Deposition rates increase and then saturate with TEOS concentration, suggesting rate-limited behavior associated with lack of ozone.