Semiconductor device and method for manufacturing the same

A semiconductor device, comprising:

• nanostructures stacked over a substrate in a vertical direction, wherein the nanostructures comprise a first nanostructure, and the first nanostructure comprises:
• a first end portion having a first inner side surface;
• a second end portion having a second inner side surface facing the first inner side surface;
• and
• a middle portion laterally between the first end portion and the second end portion;
• a first gate spacer and a second gate spacer covering the first end portion and the second end portion of the first nanostructure respectively;
• and
• a silicon germanium layer extending from the first inner side surface of the first end portion of the first nanostructure to the second inner side surface of the second end portion of the first nanostructure.

A method for manufacturing a semiconductor device, comprising:

• alternatingly stacking first epitaxial layers and second epitaxial layers over a substrate in a vertical direction;
• patterning the first epitaxial layers and the second epitaxial layers to form a fin structure;
• removing the first epitaxial layers of the fin structure thereby forming nanostructures from the second epitaxial layers of the fin structure;
• recessing middle portions of the nanostructures to form recessed middle portions of the nanostructures;
• forming silicon germanium layers around the recessed middle portions of the nanostructures;
• and
• forming a gate structure around the silicon germanium layers.