Smoothing surface roughness of iii-v semiconductor fins formed from silicon mandrels by regrowth

A method of forming a III-V semiconductor vertical fin, comprising:

• forming a fin mandrel on a substrate;
• forming a spacer layer on the substrate surrounding the fin mandrel;
• forming a wetting layer on each of the sidewalls of the fin mandrel;
• forming a fin layer on each of the wetting layers, where the fin layer is a binary or ternary III-V semiconductor material;
• removing the fin mandrel;
• removing the wetting layer on each of the fin layers;
• forming a fin layer regrowth on each of the sidewalls of the fin layers exposed by removing the wetting layer from each of the fin layers;
• and
• forming a dummy gate layer over a middle section of a vertical fin including the fin layer regrowth and the fin layer.