Semiconductor structure and method for forming the same

A method for forming a semiconductor structure, comprising:

• forming a nanosheet stack over a substrate, wherein the nanosheet stack comprises a plurality of nanosheets;
• forming a sacrificial gate structure over the nanosheet stack;
• forming epitaxial source/drain structures at two sides of the sacrificial gate structure;
• removing a portion of the sacrificial gate structure to form a first recess exposing the nanosheet stack;
• removing portions of the nanosheet stack to form a second recess coupled to the first recess;
• forming spacers on sidewalls of the first recess and sidewalk of the second recess;
• removing a portion of the substrate to form a third recess coupled to the second recess;
• and
• filling the third recess, the second recess and the first recess to form a first isolation.

A method for forming a semiconductor structure, comprising:

• receiving a substrate, wherein at least a multi-gate FET device is disposed over the substrate, and the multi-gate FET device comprises a plurality of nanosheets stacked over the substrate and separated from each other, a metal gate structure surrounding each of the nanosheets, and epitaxial source/drain structures:
• removing a portion of the metal gale structure to form a first recess, wherein portions of the nanosheets are exposed through the first recess;
• removing the portions of the nanosheets exposed through the first recess;
• removing a portion of the substrate to form a second recess coupled to the first recess;
• and filling the second recess and the first recess to form a first isolation.