Following the discovery of the bipolar transistor and the development of the MOS transistor the need for numerical models to simulate the physical behaviour of semi-conductors grew considerably. The tasks involved are complex and many models and discretization methods have been proposed. The drift-diffusion model is one of the simplest but is nevertheless of great importance. Conventional discretization methods are unsuitable for obtaining a solution and in addition the computing time required to produce results of acceptable accuracy is too great.
