Epitaxial buffer layer for finfet source and drain junction leakage reduction

A method of forming a semiconductor device comprising:

• forming a plurality of fin structures from a bulk semiconductor substrate, wherein a length of a sidewall for each fin structure of the plurality of fin structures extends from the upper surface of the fin structure to a recessed surface of a bulk semiconductor substrate present between adjacent fin structures of the plurality of fin structures;
• forming an undoped epitaxial semiconductor material on the plurality of fin structures, wherein a first portion of undoped epitaxial semiconductor material is formed on at least a portion of the sidewall a source region portion and a drain region portion of the plurality of fin structures, and a second portion of the undoped epitaxial semiconductor material is formed on the recessed surface of the bulk semiconductor substrate that is present between the adjacent fin structures;
• and
• forming a doped epitaxial semiconductor material on the undoped epitaxial semiconductor material, wherein the undoped epitaxial semiconductor material and the doped epitaxial semiconductor material provide a merged source region and a merged drain region to the adjacent fin structures of the semiconductor device.

A semiconductor device comprising:

• a gate structure on the channel region portion of a fin structure;
• at least one of an epitaxial source region and an epitaxial drain region on a source region portion and a drain region portion of the fin structure, wherein at least one of the epitaxial source region portion and the epitaxial drain region portion include a first concentration doped portion adjacent to the fin structure, and a second concentration doped portion on the first concentration doped portion, wherein the second concentration portion has a greater dopant concentration than the first concentration doped portion;
• and
• an extension dopant region extending into the channel portion of the fin structure having an abrupt dopant concentration gradient of n-type or p-type dopants of 7 nm per decade or greater.