Epitaxial Blocking Layer for Multi-Gate Devices and Fabrication Methods Thereof

A method of manufacturing a multi-gate device, comprising:

• providing a semiconductor substrate;
• forming a blocking layer in contact with the semiconductor substrate, wherein the blocking layer has a higher resistance than the semiconductor substrate;
• forming a buffer layer in contact with the blocking layer, wherein the buffer layer has a lower resistance than the blocking layer;
• forming a plurality of semiconductor nanosheets above the buffer layer;
• forming an epitaxial source/drain (S/D) feature in contact with the plurality of semiconductor nanosheets;
• and
• forming a gate structure wrapping each of the plurality of semiconductor nanosheets.

A method of manufacturing a semiconductor device, comprising:

• providing a semiconductor substrate;
• forming a blocking layer above the semiconductor substrate;
• forming a buffer layer above the blocking layer;
• forming a semiconductor layer above the buffer layer;
• patterning the semiconductor layer and the buffer layer to form a fin-shaped structure;
• etching the fin-shaped structure and the blocking layer in a source/drain (S/D) region, thereby forming an S/D trench and exposing the semiconductor substrate in the S/D trench;
• and
• epitaxially growing an S/D feature in the S/D trench, wherein the S/D feature adjoins the fin-shaped structure.