A kinetic model based on the collision theory of chemical reactions, statistical physics, and the concept of competitive adsorption is proposed for Si1-xGex growth from SiH4 and GeH4 by chemical vapor deposition. It takes into account both homogeneous and heterogeneous reactions, which involve the precursors (SiH4 and GeH4) and the homogeneous decomposition product of germane, germylene (GeH2), and three types surface sites, silicon sites, hydrogen-terminated silicon sites, and germanium sites. The growth of Si 1-xGex can be divided into two regimes: a heterogeneous decomposition dominated regime and a homogeneous decomposition dominated regime. Analytical equations are derived to quantitatively describe growth rate as a function of deposition conditions, including deposition temperature, silane flow rate, and germane flow rate, for the heterogeneous regime. Homogeneous decomposition of germane into germylene causes precursor depletion, and an empirical linear relation is employed to describe the growth behavior in the homogeneous regime. The model agrees well with the experimental data. Copyright The Electrochemical Society.