Patent ID: 8692318

Claim:
A trench MOS structure, comprising: a substrate of a first conductivity type and having a first side and a second side opposite to said first side; an epitaxial layer of said first conductivity type disposed on said first side; a trench disposed in said epitaxial layer; a gate isolation covering an inner wall of said trench; a trench gate disposed in said trench, of said first conductivity type, and of a first depth; a source of said first conductivity type, disposed within said epitaxial layer and adjacent to said trench gate; a guard ring of a second conductivity type disposed within said epitaxial layer and adjacent to said source so that said source is directly sandwiched between said guard ring and said trench gate; a reinforcement structure of a second depth having an electrically insulating material and disposed within said guard ring; and a drain disposed on said second side.