Patent ID: 7791162

Claim:
A semiconductor structure, comprising: a slab of semiconducting material having a surface and a buried layer which extends parallel to the surface, the buried layer having an upper surface and a lower surface; and a trench groove extending at least from the surface through the buried layer down to a part of the slab below the buried layer and the trench groove including a liner of a first insulating material on a wall of the trench groove, and wherein a remaining part of the trench groove is at least partially filled with a first filler material configured to provide trench isolation, and wherein the liner is characterized by an abrupt increase in thickness in at least a first part of the trench groove that is substantially in line with the buried layer, the abrupt increase in thickness defining a thickness that is larger than a thickness of the liner in a second part of the trench groove, the second part of the trench groove located below the first part.