General approach for development of CAD-oriented analytical device models

Accuracy and simplicity of analytical device models are fundamental requisites in circuit simulation and particularly crucial for current VLSI technologies. A model to be used in a circuit simulator is usually developed starting from a zero-order physically based model and adding several empirical parameters derived from a fitting procedure. In this semi-empirical scheme, however, no criteria are posed to satisfy the previously mentioned requisites. The authors provide a general approach for developing efficient device models in terms of accuracy and simplicity. For this purpose a fundamental definition of good approximation based on a given condition on the error between model and measured data is proposed and a measure for complexity of the model is defined. On the basis of these general concepts it is shown that under general conditions it is possible to derive a piecewise continuous function (PCF) from a zero-order model as a good approximation of measured data. Conditions to obtain a representation with minimum complexity are also provided