Patent ID: 7981802

Claim:
A method comprising: forming a trench over a substrate; forming a liner insulating layer over the trench; depositing a gap-fill insulating layer over said liner insulating layer; performing a first chemical mechanical polishing over said gap-fill insulating layer to expose a portion of said liner insulating layer; removing said exposed portion of said liner insulating layer by etching; and performing a second chemical mechanical polishing over said gap-fill insulating layer, wherein said forming the trench includes: growing a pad oxide layer over the substrate, wherein the substrate comprises a semiconductor substrate; growing a pad nitride layer over said pad oxide layer; depositing a hard mask layer over said pad nitride layer; and patterning at least one of said hard mask layer, said pad nitride layer and said pad oxide layer to form the trench, and wherein during said second chemical mechanical polishing, said hard mask layer, a portion of said liner insulating layer and a portion of said gap filling insulating layer are removed such that said pad nitride layer is exposed.