1. Introduction

At the end of the 20-th century microelectronics has moved into almost all areas of life. The world semiconductor sales have reached an order of 130 billion US$ consisting mainly of five product fields (automotive electronics, computer, consumer electronics, industrial electronics, telecommunication).

The multitude of applications and the strong competition in the market require fast, cheap and efficient methods for the development and optimization of new technologies and designs. During the last years Computer-Aided Design (CAD) methods have been introduced because they meet all these requirements. They simplify the developing process and therefore the time to market for new products.

Electronic CAD (ECAD) tools are used to design integrated circuits (IC) in terms of behavioral descriptions, net lists, schematics, and layout. ICs are modeled as a whole or as a set of functional blocks. In contrast the development and optimization of new technologies mainly concentrates just on a single device (transistor, diode, etc.). A deep insight into the working behavior of a single device is necessary, and it is important to know how certain production processes influence this behavior. Technology CAD (TCAD) covers this field by providing tools for the simulation of production processes and of the electrical behavior of devices. By combining process and device simulation in a TCAD frameworks the influce of process parameters on the electrical characteristics can be analyzed and optimized.

Nowadays one-dimensional and two-dimensional process simulators are used in industry, but with increasing computer performance three-dimensional simulations become more important, especially since shrinking device dimensions bring up more and more three-dimensional effects which cannot be investigated by two-dimensional simulations.