Patent ID: 8822304

Claim:
A method comprising: providing a semiconductor substrate; and performing at least two etching processes to form a trench in the semiconductor substrate, wherein the performing the at least two etching processes includes: performing a first etching process to form a first trench portion extending from a top surface of the semiconductor substrate to a first depth in the semiconductor substrate, wherein the first trench portion has a width that tapers from a first width at the surface of the semiconductor substrate to a second width at the first depth, the first width being greater than the second width, and performing a second etching process to form a second trench portion and a third trench portion, the second trench portion extending from the first depth to a second depth in the semiconductor substrate, wherein the second trench portion has substantially the second width from the first depth to the second depth, and the third trench portion extending from the second depth to a third depth in the semiconductor substrate, wherein the third trench portion has a width that tapers from the second width at the second depth to a third width at the third depth, the second width being greater than the third width, wherein the third trench portion is defined by a first sidewall extending from the second depth to the third depth and an opposing second sidewall extending from the second depth to the third depth such that the first sidewall intersects the second sidewall at the third depth, wherein an entire length of the first sidewall extending from the second depth to the third depth is transverse to the top surface of the semiconductor substrate; and filling the trench with a material.