The gas phase deposition of Si on a Si(I 0 0) surface in the presence of hydrogen was studied with three-dimensional kinetic Monte Carlo (KMC) simulations. The KMC model here proposed explicitly accounts for the 2 x 1 Si surface reconstruction and includes the reactions of adsorption of Si and H-2, their diffusion on the surface and the desorption of molecular hydrogen. Several parameters, such as the energy of interaction of adsorbed Si and H atoms, as well as the kinetic constants for the desorption of H, were calculated with density functional theory using B3LYP functionals. In particular, the activation energies for the diffusion of H along and across the dimer rows were calculate to be 2.3 and 1.8 eV, respectively. The KMC model was used to simulate the molecular beam epitaxy of Si. The activation energy and pre-exponential factor for the diffusion of Si adatoms along the dimer rows giving the best agreement with experimental data were 0.825 eV and 10(13) s(-1). The TPD of hydrogen from Si(100)2 x 1 surfaces was simulated with success using a literature kinetic constant but could not be reproduced using the single site kinetic constant calculated through quantum chemistry. Finally, it was found that adsorbed H can significantly influence the morphology evolution of the film during the growth process. (C) 2004 Elsevier B.V. All rights reserved.