State-of-the-art devices are characterized by the occurence of large gradients in the electric field. Due to the complex doping profiles which utilize ultrashallow junctions to obtain an optimum tradeoff between short-channel effects and parasitic resistances, two-dimensional numerical simulation of these structures is mandatory. From the modeling point of view, nonlocal and quantum effects gain more and more importance which need to be properly accounted for. We review the requirements for successful numerical simulation of these semiconductor devices. In addition, we give an overview of recent activities concerning device calibration and inverse modeling since inverse modeling of the doping profile in conjunction with calibration of the model parameters has proven to be an effective method of two-dimensional doping profile extraction.