The computational modeling of vapor phase processes Like CVD involves different routes. For complex chemical systems, thermodynamic analysis can be first performed. Three examples on the CVD of refractory metal disilicides and ternary silicides show the process guidelines which can be obtained from an a priori thermodynamic analysis even in feature scale technology. However, it is a static analysis. Linking the thermodynamic approach with mass transport modeling allows the description of the dynamic chemical system in local thermochemical equilibrium (LTCE). TWO examples on the deposition of titanium silicide and silicon-germanium alloys illustrate the framework provided by this approach keeping in mind the assumptions that underlie the computations. Thermodynamic and LTCE transport modeling are to be seen as an a priori computational methods based on the access of only thermodynamic and transport database.