This book is proposed to develop an SOI (Silicon on Insulator) LDMOS in which a drift region of 1-?m is added to a conventional n-MOS and compare them on various aspects. The drift region utilizes the RESURF effect that is utilized to distribute the electric field into the LDD region. It is found using two dimensional simulations that the addition of a drift region of 1-?m in LDMOS improves the performance of the device in terms of breakdown-voltage and switching-speed over the conventional MOSFET.