Methods, apparatus, and systems for forming a semiconductor substrate comprising a well region containing a first impurity; forming a gate on the semiconductor substrate above the well region; implanting a second impurity, of a type opposite the first impurity, in the well region on each side of the gate and to a depth above a bottom of the well region, to form two second impurity regions each having a first concentration; removing an upper portion of each second impurity region, to yield two source/drain (S/D) cavities above two depletion regions; and growing epitaxially a doped S/D region in each S/D cavity, wherein each S/D region comprises the second impurity having a second concentration greater than the first concentration.