A mathematical model has been developed to explore the low pressure chemical vapor deposition (LPCVD) of silicon dioxide from diethylsilane (DES)/oxygen in a horizontal hot-wall reactor. We propose a new kinetic mechanism that includes realistic gas-phase and surface reactions. The partial differential equations in two-dimensional cylindrical coordinates are solved numerically by a control-volume-based finite difference method. The model successfully describes the behavior of the experimental data. Film growth rate and uniformity are studied over a wide range of operating conditions including deposition temperature, pressure, reactant flow rate, and distance between the inlet and the wafer. The predicted results show that parasitic gas-phase reactions become significant at higher pressures and temperatures resulting in a decrease in deposition rate. It is seen that the deposition rate becomes a maximum at the O₂/DES ratio of around 2.5. A temperature of 475℃, a pressure of 0.75 torr, and a total now rate of 1,000 sccm are found to be desirable for obtaining both high deposition rate and good film uniformity.