US Patent 7772673 Deep trench isolation and method for forming same

According to one exemplary embodiment, a semiconductor die including at least one deep trench isolation region for isolating an electronic device (for example, a bipolar device) includes a trench situated in a substrate of the semiconductor die, where the trench has sides surrounding the electronic device, and where the trench has at least one trench chamfered corner formed between and connecting the sides of the trench. The at least one trench chamferred corner is formed between a chamfered corner of an outside wall of said trench and a corner of an inside wall of the trench. A trench corner width at the at least one trench chamfered corner is less than a trench side width along the sides of the trench.