Patent ID: 8120137

Claim:
A semiconductor device comprising: a substrate; and an isolation trench structure, comprising: a first isolation trench portion associated with a surface of the substrate, wherein the first isolation trench portion includes a first pair of opposing sidewalls that are each substantially perpendicular to the surface of the substrate; a spacer of a predetermined thickness on the sidewalls and a bottom of the first isolation trench portion that confines an in situ etch of a second isolation trench portion to a predetermined smaller area; the second isolation trench portion including a second pair of sidewalls within the substrate that are each angled obliquely with respect to the surface of the substrate, wherein the second isolation trench portion has a separation between the second pair of sidewalls that decreases as a distance from the first isolation trench portion increases; and a third isolation trench portion including a third pair of sidewalls within the substrate that are each substantially perpendicular to the surface of the substrate.