Wrap-around trench contact structure and methods of fabrication

A wrap-around source/drain trench contact structure is described. A plurality of semiconductor fins extend from a semiconductor substrate. A channel region is disposed in each fin between a pair of source/drain regions. An epitaxial semiconductor layer covers the top surface and sidewall surfaces of each fin over the source/drain regions, defining high aspect ratio gaps between adjacent fins. A pair of source/drain trench contacts are electrically coupled to the epitaxial semiconductor layers. The source/drain trench contacts comprise a conformal metal layer and a fill metal. The conformal metal layer conforms to the epitaxial semiconductor layers. The fill metal comprises a plug and a barrier layer, wherein the plug fills a contact trench formed above the fins and the conformal metal layer, and the barrier layer lines the plug to prevent interdiffusion of the conformal metal layer material and plug material.