The advancement of knowledge in the electronic design is strongly influenced by Technology Computer Aided Design–TCAD. Here is an interesting positive feedback, because the computing power helps the designers to perform modelling, simulation, optimisation and design of the new devices with improved performance, which have the capability to increase the computing power. The chapter present the basic aspects and the state-of-the-art of processes and devices modelling completed with the new aspects presented by the author in their last few year’s papers like the results of his researches.