An integrated three-dimensional (3D) simulation approach for the optimization of multistep process modules is developed. A link between a 3D finite volume reactor-scale model and a developed 3D cell topography feature-scale model allows the prediction of uniformity distribution for a sequence of process steps on an entire wafer surface. As an example, an across-wafer gap-fill is simulated using a combination of simulation tools to capture a variety of nonuniformities that exist in all steps involved in the local interconnect tungsten-fill process flow. Across-wafer variations in Ti flux density, angular distributions in Ti and TiN physical vapor deposition fluxes, as well as nonuniformities in precursor fluxes in TiN and W chemical vapor deposition are taken into consideration. Across wafer blanket layer thickness variations as well as bottom and sidewall thickness variations inside interconnect features are determined for all deposited layers. Across-wafer metal stack thickness distributions, wafer edge effect, and key-hole formation inside the features are simulated. Experimentally extracted parameters are employed for the calibration of the simulation results.