If the 1980s were the decade in which two-dimensional (2-D) device simulation became widely used for device design, the 1990s saw the widespread adoption of 2-D process simulation. Physics-based models of such processes as ion channeling, transient enhanced diffusion and surface dopant loss, coupled with much faster workstations and large memories, have put predictive capability on process engineer's desktops. Sophisticated modeling strategies combined with focused experiments have led to the improved physical understanding of dopant implantation, diffusion and activation. A hierarchy of tools, from ab-initio electronic structure calculations, through Monte Carlo diffusion simulators, to the continuum models which are the mainstay of process design, have been applied. The implications of some of these newly discovered phenomena are analyzed in a number of applications in advanced technologies.