Patent ID: 7488642

Claim:
A method of making a buried plate region in a substrate including a single-crystal semiconductor region, comprising: etching the substrate to pattern a trench elongated in a direction extending downwardly into the single-crystal semiconductor region, the trench having a trench sidewall, the trench sidewall having an upper portion adjacent to a major surface of the substrate and a lower portion disposed below the upper portion at greater depth from the major surface; forming a dopant source layer overlying the lower portion of the trench sidewall, the dopant source layer not overlying an upper portion of the trench sidewall; selectively epitaxially growing a layer consisting essentially of semiconductor material onto the single-crystal semiconductor region exposed at the upper portion of the trench sidewall above the dopant source layer; while the epitaxially grown layer overlies the upper portion, annealing to drive a dopant from the dopant source layer into the single-crystal semiconductor region adjacent to the lower portion to form a buried plate; removing the dopant source layer; and forming an isolation collar along at least a part of the upper portion after removing the dopant source layer.