A method is provided for making a buried plate region in a semiconductor substrate. According to such method, a trench is a single-crystal semiconductor region of a substrate is etched to form a trench elongated in a direction extending downwardly from a major surface of the substrate. A dopant source layer is formed to overlie a lower portion of the trench sidewall but not an upper portion of the trench sidewall. A layer consisting essentially of semiconductor material is epitaxially grown onto a single-crystal semiconductor region exposed at the upper portion of the trench sidewall above the dopant source layer. Through annealing, a dopant is then driven from the dopant source layer into the single-crystal semiconductor material of the substrate adjacent to the lower portion to form a buried plate. Then, the dopant source layer is removed and an isolation collar is formed along at least a part of the upper portion.