Semiconductor devices and methods of manufacture thereof are disclosed. In a preferred embodiment, a semiconductor device includes a workpiece having a buried layer disposed beneath a top portion of the workpiece. An isolation ring structure is disposed within the top portion of the workpiece extending completely through at least a portion of the buried layer, the isolation ring structure comprising a ring having an interior region. A diffusion confining structure is disposed within the interior region of the isolation ring structure. A conductive region is disposed within the top portion of the workpiece within a portion of the interior of the isolation ring structure, the conductive region comprising at least one dopant element implanted and diffused into the top portion of the workpiece. The diffusion confining structure defines at least one edge of the conductive region, and the conductive region is coupled to the buried layer.