Patent ID: 8461661

Claim:
A protection structure that protects an isolation trench, the isolation trench being formed in a substrate, the isolation trench having opposite first and second side walls and having polysilicon therein with opposite first and second outermost side boundaries adjacent the first and second side walls, respectively, such that the first outermost side boundary is nearer to the first side wall than the second side wall, and the second outermost side boundary is nearer to the second side wall than the first side wall, the protection structure comprising: an oxide layer on the polysilicon and the substrate; and a silicon nitride cap on the oxide layer over the polysilicon, the silicon nitride cap extending from a first outermost lateral boundary situated laterally between the first outermost side boundary of the polysilicon and the first side wall of the isolation trench, and the silicon nitride cap extending to a second outermost lateral boundary situated laterally between the second outermost side boundary of the polysilicon and the second side wall of the isolation trench.