A semiconductor device includes a plurality of first conductivity type semiconductor nanowire cores located over a support and extending from portions of a semiconductor surface of the support exposed through openings in the insulating mask layer, and a plurality of semiconductor shells extending over the respective nanowire cores. Each of the plurality of semiconductor shells includes at least one semiconductor interior shell extending around the respective one of the plurality nanowire cores, and a second conductivity type semiconductor outer shell extending around the at least one semiconductor interior shell. A first electrode layer contacts the second conductivity type semiconductor outer shell of the plurality of semiconductor shells and extends into spaces between the semiconductor shells. The semiconductor interior shell includes a semiconductor foot portion which extends under the first electrode and under the respective second conductivity type semiconductor outer shell on the insulating masking layer in the spaces between the plurality of semiconductor shells.