Abstract
Conventional VDMOSFET (Vertical Double diffused Metal Oxide Semiconductor Field Effect Transistor) technology for power devices was constrained by the Silicon Limit. This is now improved to have linear relation between on resistance (Ron) and breakdown voltage(BV) instead of the quadratic relation. In 1998, for the first time the new device concept for high voltage power devices which is called super-junction theory has been realized in silicon. We have designed SJ-layer based on this theory in this thesis and used it to construct the SJ-MOSFET : CoolMOS structure. The claim of the theory that the doping level of the drift region can be increased by at least one order of magnitude, at least 5 times improvement in on resistance without reducing the BV. The effect of charge imbalance created due to the neck region of power MOSFET is also investigated in the thesis.