Source and Drain Surface Treatment for Multi-Gate Field Effect Transistors

A method of forming a field effect transistor (FET), comprising:

• providing a semiconductor substrate and a fin extending from the semiconductor substrate and through an isolation structure covering the semiconductor substrate, the fin including a first semiconductor material and having a source region, a channel region, and a drain region for the FET;
• forming a gate stack over the channel region;
• performing an oxidization process on top and sidewall surfaces of the fin in the source and drain regions;
• performing an etching process on the oxidized top and sidewall surfaces of the fin in the source and drain regions;
• repeating the performing of the oxidization process and the performing of the etching process until a width of the fin in the source and drain regions is reduced by a predetermined value;
• and
• epitaxially growing a material layer covering the fin in the source and drain regions.

A method, comprising:

• providing a substrate and a fin extending from the substrate and through an isolation structure covering the substrate, wherein the fin includes a source region, a channel region, and a drain region for a transistor;
• forming a gate stack over the channel region;
• oxidizing top and sidewall surfaces of the fin in the source and drain regions;
• etching the oxidized top and sidewall surfaces of the fin to shrink a width and a height of the fin in the source and drain regions, wherein the sidewall surfaces of the fin in the source and drain regions are curved after the etching;
• and
• epitaxially growing a material layer covering the fin in the source and drain regions.