Patent ID: 8269307

Claim:
A Shallow Trench Isolation (STI) structure, comprising: a semiconductor substrate; a first trench formed on the upper surface of the semiconductor substrate and filled with an epitaxial layer, wherein the upper surface of the epitaxial layer is higher than that of the semiconductor substrate; and a second trench formed on the epitaxial layer and filled with a first dielectric layer, wherein the upper surface of the first dielectric layer is flushed with that of the epitaxial layer, and the width of the second trench is smaller than that of the first trench; and wherein the epitaxial layer comprises a first epitaxial layer and a second epitaxial layer located thereon; and wherein the material of the first epitaxial layer is different from that of the semiconductor substrate, and the material of the second epitaxial layer is the same as that of the semiconductor substrate.