A semiconductor device herein includes doped extension regions for silicon and silicon germanium nanowires. The nanowires can be selectively grown and recessed into a gate spacer. The semiconductor device can include a gate structure including the gate spacer; the nanowire or channel extending through the gate structure such that an end of the channel is recessed within a recess in said gate spacer; an extension region in contact with the end of the channel within the recess, the extension region being formed of an extension material having a different composition than a channel material of the channel such that a strain is provided in the channel; and a source-drain contact in contact with the extension region and adjacent to the gate structure.