Patent ID: 7479688

Claim:
A semiconductor structure comprising: a first semiconductor active area having, and laterally surrounded by, a first sidewall and located in a semiconductor substrate; a first trench isolation region laterally abutting said first sidewall and surrounding said first semiconductor active area and comprising silicon oxide, wherein a first portion of a bottom surface of said first trench isolation region and said first sidewall does not contact any nitride liner; a second semiconductor active area having, and laterally surrounded by, a second sidewall and located in said semiconductor substrate; a nitride liner laterally abutting said second sidewall and a second portion of said first trench isolation region, wherein said second portion laterally abuts said first portion, and wherein an edge of said nitride liner is located at a bottom surface of said first trench isolation region underneath a boundary between said first portion and said second portion; and a second trench isolation region laterally abutting said nitride liner and surrounding said second semiconductor active area and comprising silicon oxide, wherein another edge of said nitride liner is located at a bottom surface of said second trench isolation region.