Patent ID: 11961919
Assignee: TAIWAN SEMICONDUCTOR MANUFACTURING COMPANY LTD.
Field: Semiconductors (Electrical engineering)
Classification: CPC H  B | IPC H

Claim 7:
8. A method of forming a semiconductor device, the method comprising:
forming a fin over a substrate, the fin comprising a layer stack and a semiconductor layer underlying the layer stack, the layer stack comprising alternating layers of a first semiconductor material and a second semiconductor material;
forming a dummy gate structure over the fin;
forming source/drain regions over the fin on opposing sides of the dummy gate structure; and
replacing the dummy gate structure with a replacement gate structure, wherein replacing the dummy gate structure comprises:
removing the dummy gate structure to expose the first semiconductor material and the second semiconductor material disposed under the dummy gate structure;
removing the exposed first semiconductor material, wherein after removing the exposed first semiconductor material, the second semiconductor material remains to form channel regions of the semiconductor device;
after removing the exposed first semiconductor material, reshaping middle portions of the channel regions while keeping end portions of the channel regions intact, wherein the end portions of the channel regions contact the source/drain regions, and the middle portions are between respective ones of the end portions, wherein removing the exposed first semiconductor material is performed using a first etchant selective to the first semiconductor material, wherein the first etchant is a first etching gas comprising F2 and HF, wherein reshaping the middle portions of the channel regions is performed using a second etchant selective to the second semiconductor material, wherein the second etchant is a second etching gas comprising a mixture of NF3 and NH3;
forming a gate dielectric material around the channel regions; and
forming a gate material around the gate dielectric material.