A method of forming a semiconductor device that may include etching source and drain portions of a fin structure of a first semiconductor material selectively to an underlying semiconductor layer of a second semiconductor material, and laterally etching undercut region in the semiconductor layer underlying the fin structure. The method may further include filling the undercut region with a first conductivity type semiconductor material, and forming a second conductivity type semiconductor material for a source region and a drain region on opposing sides of the channel region portion of the fin structure.