Power semiconductor devices having laterally extending base shielding regions that inhibit base reach-through

Abstract

A power MOSFET includes a semiconductor substrate having a drift region therein and a transition region that extends between the drift region and a first surface of the semiconductor substrate. The transition region has a vertically retrograded doping profile therein that peaks at a first depth relative to the first surface. An insulated gate electrode is provided that extends on the first surface and has first and second opposing ends. First and second base regions of second conductivity type are provided in the substrate. The first and second base regions are self-aligned to the first and second ends of the insulated gate electrode, respectively, and form respective P-N junctions with opposing sides of an upper portion of the transition region extending adjacent the first surface. First and second source regions are provided in the first and second base regions, respectively. First and second base shielding regions are also provided and these regions are more highly doped and formed deeper than the first and second base regions. The first and second base shielding regions also extend laterally towards each other in the substrate to thereby constrict a neck of the upper portion of the transition region to a minimum width at a second depth relative to the first surface that is deeper than the first and second base regions.