III-V materials can play a major role along with Si in future logic and analog submicron devices. In this book, new approaches and designs of GaN-MESFET called multigate GaN-MESFETs and their 2-D analytical and numerical analysis have been proposed and investigated in order to improve the SCEs for future power switching and digital gate devices. It has been analyzed that the Dual Material design offers superior characteristics as compared to single material gate devices. In addition, MOGAs- based approaches are proposed to optimize the different designs in term of subthreshold and analog performances for high speed submicron digital applications and to search for optimal electrical and dimensional parameters to obtain better electrical performance of the device for analog and digital circuit applications