Silicon film deposition by silence decomposition in LPCVD(Low Pressure Chemical Vapor Deposition) process has been simulated by numerical computation of the governing transport and reaction equations, assuming that the rate of silane decomposition in the gas phase controls the overall film growth rate. The film grouch rate and the film uniformity increase with the reattain flow rate when the flow rate is restively low, but they decrease at higher flow rates due to the negalive effect of the reduced reaction time in the reactor. Accordingly, the film deposition process is optimized 1y controlling the reactants flow rate so that the position of the maximum SiH₄-decomposition rate in the gas phase is located above the substrate region. With a larger degree of the substrate tilting, the growth rate decreases but the film uniformity is improved. The film uniformity is also improved when the pressure is low.