Trench-gated device having trench walls formed by selective epitaxial growth and process for forming device

Abstract

An improved trench-gated power device comprises a substrate having an overlying layer of epitaxial material disposed on an upper layer of the substrate, well regions containing source and body regions, a trench gate, and a drain region. The improvement comprises a gate trench having beneficially smooth sidewalls that comprise selectively grown epitaxial material and body regions that are recessed with respect to adjacent source regions. In a process for forming an improved trench-gated power device, a dielectric layer having an upper surface and thickness and width dimensions that substantially correspond to the height and width dimensions of a gate trench is formed on an upper layer of the substrate. A layer of epitaxial material is grown on the upper layer of the substrate and the dielectric layer and planarized to be substantially coplanar with the upper surface of the dielectric layer, which is then removed, thereby forming gate trench sidewalls that comprise selectively grown epitaxial material. The process further comprises lining the trench with a dielectric material and substantially filling the lined trench with a conductive material, thereby forming a trench gate, and forming well, body, and source regions in the planarized epitaxial material.