Patent ID: 8159021

Claim:
A trenched semiconductor power device comprising a plurality of trenched gates surrounded by source regions near a top surface of a semiconductor substrate encompassed in body regions, said trenched semiconductor power device further comprising: a first epitaxial layer of a first conductivity type disposed above a heavily doped substrate and extends above a bottom surface of the trenched gates and a second epitaxial layer of the first conductivity type disposed above said first epitaxial layer wherein a resistivity N 1 of said first epitaxial layer is greater than a resistivity N 2 of said second epitaxial layer represented by a functional relationship of N 1 >N 2 ; each of said trenched gates includes an upper gate portion and lower gate portion wherein said lower gate portion is surrounded with a lower gate insulation layer having a greater thickness than an upper gate insulation layer surrounding said upper gate portion; and said body regions of a second conductivity type interfacing with said second epitaxial layer constituting P/N junctions wherein said P/N junctions disposed above said lower gate portion surrounded by said lower insulation layer having a greater thickness formed on sidewalls of said trenched gates and said lower gate insulation layer interfaces with said upper gate insulation layer at a vertical level surrounded by said second epitaxial layer having the lower resistivity N 2 but below each of said P/N junctions.