Nanosheet field-effect transistor device and method of forming

A method of forming a semiconductor device, the method comprising:

• forming a first gate structure over a nanostructure, wherein the nanostructure comprises layers of a first semiconductor material interleaved with layers of a second semiconductor material, wherein the nanostructure is disposed over a fin;
• forming recesses in the nanostructure on opposing sides of the first gate structure;
• removing portions of the first semiconductor material exposed by the recesses to form first sidewall recesses;
• lining the recesses and the first sidewall recesses with a multi-layer spacer film, wherein the multi-layered spacer film comprises a first spacer layer and a second spacer layer that are formed of different materials;
• performing a first dry etch process to remove first portions of the first spacer layer and first portions of the second spacer layer that are disposed outside the first sidewall recesses;
• and
• after performing the first dry etch process, performing a second dry etch process to remove second portions of the second spacer layer from the first sidewall recesses, wherein the first dry etch process and the second dry etch process are performed using different etching gases.

A method of forming a semiconductor device, the method comprising:

• forming a nanostructure over a fin, the nanostructure comprising alternating layers of a first semiconductor material and a second semiconductor material;
• forming a first gate structure over the nanostructure;
• forming source/drain openings extending into the nanostructure on opposing sides of the first gate structure;
• recessing portions of the first semiconductor material exposed by the source/drain openings to form first sidewall recesses;
• conformally and successively forming a first spacer layer and a second spacer layer in the source/drain openings and in the first sidewall recesses;
• performing a trimming process to remove first portions of the first spacer layer and first portions of the second spacer layer disposed outside the first sidewall recesses, wherein the trimming process is an etching process performed using a first etchant;
• after performing the trimming process, performing a cleaning process, wherein the cleaning process selectively removes second portions of the second spacer layer disposed in the first sidewall recesses, wherein the cleaning process is a dry etch process performed using a second etchant different from the first etchant;
• and
• forming source/drain regions in the source/drain openings, wherein air gaps are formed between the source/drain regions and remaining portions of the first spacer layer in the first sidewall recesses.