A method of forming a semiconductor device that includes forming a fin structure from a bulk semiconductor substrate and forming an isolation region contacting a lower portion of a sidewall of the fin structure, wherein an upper portion of the sidewall of the fin structure is exposed. A sacrificial spacer is formed on the upper portion of the sidewall of the fin structure. The isolation regions are recessed to provide an exposed section of the sidewall of the fin structure. A doped semiconductor material is formed on the exposed section of the lower portion of the sidewall of the fin structure. Dopant is diffused from the doped semiconductor material to a base portion of the fin structure.