Threshold voltage adjustment for a gate-all-around semiconductor structure

A method, comprising:

• providing a semiconductor structure that includes a plurality of first semiconductor layers and a plurality of second semiconductor layers, the first and second semiconductor layers having different material compositions and are alternatingly disposed with respect to each other in a vertical direction;
• forming a plurality of dummy gate stacks over an uppermost first semiconductor layer;
• removing portions of the second semiconductor layers in a first region of the semiconductor structure, thereby forming a plurality of first spaces in place of the removed portions of the second semiconductor layers in the first region;
• extending the first spaces horizontally via a lateral etching process;
• and
• thereafter removing portions of the second semiconductor layers in a second region of the semiconductor structure, thereby forming a plurality of second spaces in place of the removed portions of the second semiconductor layers in the second region, wherein remaining portions of the second semiconductor layers in the first region have different horizontal dimensions than remaining portions of the second semiconductor layers in the second region.

A method, comprising:

• forming a plurality of first semiconductor layers and a plurality of second semiconductor layers, the first semiconductor layers interleaving with, and having a different material composition than, the second semiconductor layers;
• performing a first etching process to form a plurality of voids in the second semiconductor layers but not in the first semiconductor layers;
• and
• after the first etching process is performed, performing a second etching process to increase at least a lateral dimension of each of the voids, wherein the second etching process and the first etching process have different etching parameters;
• and
• after the second etching process is performed, performing an epitaxial growth process to form a third semiconductor layers in each of the voids.