Reduction of multi-threshold voltage patterning damage in nanosheet device structure

A semiconductor integrated circuit device, comprising:

• a nanosheet field-effect transistor device disposed on a semiconductor substrate, wherein the nanosheet field-effect transistor device comprises:
• a nanosheet stack structure comprising a plurality of active nanosheet channel layers and a dummy nanosheet channel layer disposed above the active nanosheet channel layers of the nanosheet stack structure;
• and
• a metal gate structure covering the nanosheet stack structure, wherein the metal gate structure comprises:
• a conformal gate dielectric layer disposed on surfaces of each of the dummy nanosheet channel layer and the active nanosheet channel layers;
• and
• a work function metal layer formed on the conformal gate dielectric layers and filling the gate region including spaces above and below the active nanosheet channel layers and the dummy nanosheet channel layer with the work function metal layer;
• wherein the dummy nanosheet channel layer has a thickness which is less than a thickness of each of the active nanosheet channel layers, wherein the thickness of the dummy nanosheet channel layer is configured so that the dummy nanosheet channel layer does not function as an active channel layer of the nanosheet field-effect transistor device.

A semiconductor integrated circuit device, comprising:

• a first nanosheet field-effect transistor device and a second nanosheet field-effect transistor device disposed on a semiconductor substrate;
• wherein the first nanosheet field-effect transistor device comprises:
• a first nanosheet stack structure comprising a plurality of active nanosheet channel layers and a dummy nanosheet channel layer disposed above the active nanosheet channel layers of the first nanosheet stack structure;
• and
• a first metal gate structure covering the first nanosheet stack structure, wherein the first metal gate structure comprises:
• a first conformal gate dielectric layer disposed on surfaces of each of the dummy nanosheet channel layer and the active nanosheet channel layers;
• and
• a first work function metal layer disposed on the first conformal gate dielectric layers and filling the gate region including spaces above and below the active nanosheet channel layers and the dummy nanosheet channel layer of the first nanosheet stack structure with the first work function metal layer;
• wherein the dummy nanosheet channel layer of the first nanosheet stack structure has a thickness which is less than a thickness of each of the active nanosheet channel layers a first nanosheet stack structure, wherein the thickness of the dummy nanosheet channel layer is configured so that the dummy nanosheet channel layer does not function as an active channel layer of the first nanosheet field-effect transistor device;
• and
• wherein the second nanosheet field-effect transistor device comprises:
• a second nanosheet stack structure comprising a plurality of active nanosheet channel layers and a dummy nanosheet channel layer disposed above the active nanosheet channel layers of the second nanosheet stack structure;
• and
• a second metal gate structure covering the second nanosheet stack structure, wherein the metal gate structure comprises:
• a second conformal gate dielectric layer disposed on surfaces of each of the dummy nanosheet channel layer and the active nanosheet channel layers;
• and
• a second work function metal layer disposed on the second conformal gate dielectric layers and filling the gate region including spaces above and below the active nanosheet channel layers and the dummy nanosheet channel layer of the second nanosheet stack structure with the second work function metal layer;
• wherein the dummy nanosheet channel layer of the second nanosheet stack structure has a thickness which is less than a thickness of each of the active nanosheet channel layers of the second nanosheet stack structure, wherein the thickness of the dummy nanosheet channel layer is configured so that the dummy nanosheet channel layer does not function as an active channel layer of the second nanosheet field-effect transistor device.