Integrated circuit structure and method for fabricating the same

A method comprising:

• forming a semiconductor stack over a substrate, wherein the semiconductor stack comprises a first sacrificial layer, a channel layer over the first sacrificial layer, and a second sacrificial layer over the channel layer;
• patterning the semiconductor stack into a fin structure such that opposite first ends of the channel layer are exposed;
• etching the opposite first ends of the channel layer;
• forming first dummy spacers on the etched opposite first ends of the channel layer;
• forming an isolation structure in the fin structure;
• recessing a top surface of the isolation structure to a position lower than a bottom surface of the channel layer, such that opposite second ends of the channel layer are exposed;
• recessing the opposite second ends of the channel layer;
• forming second dummy spacers on the recessed opposite second ends of the channel layer;
• and
• replacing the first dummy spacers with a metal gate structure.

A method comprising:

• forming a stack over a semiconductor substrate, wherein the stack comprises a first sacrificial layer, an epitaxial layer over the first sacrificial layer, and a second sacrificial layer over the epitaxial layer, the first sacrificial layer and the second sacrificial layer comprise a first composition, the epitaxial layer comprise a second composition different from the first composition;
• patterning the stack into a fin structure such that opposite first ends of the epitaxial layer are exposed;
• recessing the opposite first ends of the epitaxial layer;
• forming first dummy spacers on the recessed opposite first ends of the epitaxial layer;
• forming an isolation structure in the fin structure;
• recessing a top surface of the isolation structure to a position lower than a bottom surface of the epitaxial layer, such that opposite second ends of the epitaxial layer are exposed;
• recessing the opposite second ends of the epitaxial layer;
• forming second dummy spacers on the recessed opposite second ends of the epitaxial layer;
• and
• replacing the first dummy spacers and the second dummy spacers with a metal gate structure.