A model of the hot wall tubular reactor for low pressure chemical vapor deposition (LPCVD) is applied to the study of silicon nitride film growth from dichlorosilane and ammonia. The model predicts the effects of process conditions and reactor configuration on distributed wafer growth rate profiles. The model formulation includes contributions from convection, multicomponent diffusion, and gas and surface reactions of several chemical species. Rival chemical mechanisms are compared to experimental data obtained in a conventional LPCVD reactor over widely varying conditions. Results indicate that the in‐wafer film thickness nonuniformities may be explained by the effect of diffusion‐limited film growth from highly reactive gas‐phase intermediates, with simultaneous uniform deposition from less reactive dichlorosilane. Model predictions agree well with experimental data over the composition, pressure, and temperature ranges considered. The model is also used in the design of optimal operating conditions for 100 and 150 mm wafer processes.