Patent ID: 7928474

Claim:
A semiconductor structure comprising: a semiconductor substrate; an insulating region extending from substantially a top surface of the semiconductor substrate into the semiconductor substrate; an embedded dielectric spacer adjacent the insulating region, wherein a bottom of the embedded dielectric spacer adjoins the semiconductor substrate, wherein an edge of the embedded dielectric spacer is substantially vertically aligned to a top tip of the insulating region, wherein the semiconductor structure further comprises a semiconductor layer horizontally between and adjoining the insulating region and the embedded dielectric spacer, and wherein the semiconductor layer and the semiconductor substrate are formed of a same material; and a semiconductor material adjoining a top edge and extending on a sidewall of the embedded dielectric spacer, wherein the semiconductor material comprises: a bottom portion comprising a top surface level with the top edge of the embedded dielectric layer; and a top portion comprising a bottom surface contacting the top surface of the bottom portion, wherein the top portion and the bottom portion comprise silicon carbon, and wherein the top portion has a higher carbon atomic percentage than the bottom portion.