Semiconductor devices and methods of fabrication are described herein. The method includes steps for patterning fins in a multilayer stack and forming an opening in a fin and into a substrate as an initial step in forming a source/drain region. A first semiconductor material is epitaxially grown from channels exposed along sidewalls of the opening to form first source/drain structures. A second semiconductor material is epitaxially grown from the first semiconductor material to form a second source/drain structure over and to fill a space between the first source/drain structures. A bottom of the second source/drain structure is located below a bottommost surface of the first source/drain structures. The second semiconductor material has a greater concentration percentage by volume of germanium than the first semiconductor material. A stack of nanostructures is formed by removing sacrificial layers of the multilayer stack, the second semiconductor material being electrically coupled to the nanostructures.