The objectives of this study are to develop a simplified reaction model for Si deposition from an SiHCl3-H-2 gas mixture, and to investigate the effect of the gas flow pattern on Si deposition in a vertical rotating disk (VRD) reactor. A well-known simplified Si deposition model involves SiHCl3 adsorption and Si production by reaction with H-2. On the other hand, it has been reported that the reactivity of HCl, which is a by-product from the SiHCl3-H-2 system, has a strong influence on the Si deposition rate. Therefore, we have modified the simplified model to include this effect of HCl concentration. Numerical simulations of momentum, energy, and mass transport in the VRD reactor were conducted using the new reaction model. When the inlet gas flow rate was insufficient, the deposited Si films had non-uniform thickness in the radial direction of the wafer. The numerical results have indicated that large-scale recirculating flow occurs in the reactor, and the byproduct HCl gas accumulates in the reactor when the inlet gas flow rate is insufficient. Therefore, the film thickness is considered to decrease from the center to the perimeter of the wafer. The proposed simplified reaction model, which explicitly takes into account the effect of HCI, is able to predict such a distribution of the Si deposition rate on the wafer surface under conditions with insufficient flow rate. (C) 2016 Elsevier B.V. All rights reserved.