A new physical-chemical model, which applies over a wide range of operating pressures, describes the gas phase and surface reactions in subatmospheric chemical vapor deposition of silicon dioxide for producing inter-layer dielectrics in a cold-wall reactor. Tetraethylorthosilicate (TEOS) reacts in the gas phase to form an intermediate which is adsorbed and reacts on the surface to produce a silicon dioxide film, The results compare favorably with experimental data over a pressure range of 100-600 Torr and a temperature range of 370-500 degrees C. The concentration distributions of TEOS, intermediate and ozone in the gas phase and their ratios at the surface of the wafer are determined to study gas phase nucleation and the relationship between composition distributions and film quality. Previous models based on low pressure data in the range of 30-90 Torr need to be modified to predict accurately the rates of deposition from 100 Torr to atmospheric pressure. Gas phase reactions cause the maximum in the deposition rates to shift to higher pressures at lower deposition temperatures, both in the model and experiments. At higher pressures, particulates are formed by the gas phase reactions which must be included to represent properly the chemical dynamics of the process. The deposition rate increases up to an asymptotic value as the TEOS flow rate is increased; above this level no further increase in growth rate occurs. This is a consequence of the basic mechanism of the surface reaction which predicts the asymptotic behavior observed.