In the context of semiconductor manufacturing, chemical vapor deposition (CVD) denotes the deposition of a solid from gaseous species via chemical reactions on the wafer surface. In order to obtain a realistic process model, this paper proposes the introduction of an intermediate scale model on the scale of a die. Its mathematical model is a reaction-diffusion equation with associated boundary conditions including a flux condition at the micro structured surface. The surface is given in general parameterized form. A homoganization technique from asymptotic analysis is used to replace this boundary condition by a condition on the flat surface to make a numerical solution feasible. Results from a mathematical test problem are included.