Method of manufacturing a semiconductor device and a semiconductor device

A semiconductor device, comprising:

• a plurality of semiconductor wires disposed over a substrate in a stack arranged along a first direction, the first direction extending substantially perpendicular to a main surface of the substrate;
• an epitaxial layer in contact with ends of the semiconductor wires;
• and
• a gate electrode layer wrapping around a channel region of the semiconductor wires,
• wherein each semiconductor wire comprises an inner layer and two opposing outer layers, wherein the inner layer and the outer layers comprise Si and Ge, and the outer layers have a greater concentration of Ge than the inner layer, and wherein a thickness of the inner layer is greater than a thickness of either of the outer layers.

A semiconductor device, comprising:

• a first plurality of nanowires and a second plurality of nanowires, wherein both of the first plurality of nanowires and the second plurality of nanowires extend along a first direction and are stacked along a second direction substantially perpendicular to the first direction;
• and
• first and second gate structures wrapped around a channel region of each nanowire of the first and second plurality of nanowires, respectively,
• wherein each nanowire of the first plurality of nanowires are composed of a first semiconductor sublayer comprising Si and Ge having a first concentration of Ge, and second semiconductor sublayers disposed on opposing sides of the first semiconductor sublayer comprising Si and Ge having a second concentration of Ge, wherein the second concentration of Ge is greater than the first concentration of Ge, and
• each nanowire of the second plurality of nanowires is composed of one of either Si or Ge.