Patent ID: 7635899

Claim:
A semiconductor structure comprising: a substrate having at least one well including a dopant; and at least one STI trench in the substrate including an upper portion of the at least one STI trench defining a width of a trench opening at a surface of the substrate, and the at least one STI trench including an oxidized porous region in the substrate adjacent a bottom portion of the at least one STI trench and the at least one STI trench is filled with a dielectric oxide, wherein the at least one STI trench includes a first STI trench defining a first opening having a first width, and a second STI trench defining a second opening having a second width, and the oxidized porous region of the first trench having a first width and a first depth, and the oxidized porous region of the second trench having a second width and a second depth.