Patent ID: 8847306

Claim:
A method for making a shield gate trench semiconductor device, comprising: a) etching a semiconductor substrate to form trenches TR 1 , TR 2 and TR 3 with three widths Wl, W 2 and W 3 , respectively, wherein the trench TR 3 is widest and deepest and the width W 3 of the trench TR 3 depends on a depth D 2 of the trench TR 2 , wherein the semiconductor substrate includes an epitaxial layer over a heavily doped substrate and wherein the trench TR 3 extends into the heavily doped substrate and the trenches TR 1 and TR 2 do not; b) forming first conductive material at the bottom of the trenches TR 1 , TR 2 and TR 3 to form a source electrode; c) forming a second conductive material over the first conductive material in the trenches TR 1 and TR 2 to form a gate electrode, wherein the first and second conductive materials are separated from each other and from the semiconductor substrate by an insulator material; d) depositing a first insulator layer on top of the trenches TR 1 , TR 2 and TR 3 , wherein a top portion of the trench TR 3 is filled up with the insulator; e) forming a body layer in a top portion of the substrate; f) forming a source layer in a top portion of the body layer; g) applying a second insulator layer on top of the trenches TR 1 , TR 2 and TR 3 and the source; h) forming a source electrode contact in trench TR 3 , a gate electrode contact in trench TR 2 , and a source/body contact to the semiconductor substrate; and i) forming source metal and gate metal on top of the second insulator layer.