Gate-all-around FETs having uniform threshold voltage

A gate-all-around field effect transistor comprising:

• at least one stack comprising a first nanosheet, a second nanosheet, a third nanosheet, an inner work function metal, and an outer work function metal, wherein the outer work function metal has been modified so as to cause an outer threshold voltage of an outer channel to be within a predefined amount of an inner threshold voltage of an inner channel in the at least one stack, wherein a first thickness of the inner work function metal between the first nanosheet and the second nanosheet is greater than a second thickness of the inner work function metal between the second nanosheet and the outer work function metal, wherein an inner edge of the outer work function metal and an outer edge of the inner work function metal both extend in parallel continually from above an uppermost one of the first, second, and third nanosheets to below a lowermost one of the first, second, and third nanosheets to an underlayer so as to be in direct contact with the underlayer, the underlayer being directly below a middle portion of the first, second, and third nanosheets and extending in a width direction beyond sides edges of the first, second, and third nanosheets, wherein a stack of materials covers and laterally surrounds the first, second, and third nanosheets.

A semiconductor device comprising:

• an N-type field effect transistor (NFET) and a P-type field effect transistor (PFET), each including an inner work function metal, an outer work function metal, a first nanosheet comprising an inner channel surface having a first threshold voltage, a second nanosheet comprising an outer channel surface having a second threshold voltage, and a third nanosheet;
• and
• additional material in the outer work function metal so as to cause the outer channel surface for the second nanosheet to have the second threshold voltage that is within a predefined amount of the first threshold voltage for the inner channel surface of the first nanosheet, wherein an inner edge of the outer work function metal and an outer edge of the inner work function metal both extend continually from above an uppermost one of the first, second, and third nanosheets to below a lowermost one of the first, second, and third nanosheets to an underlayer so as to be in direct contact with the underlayer, wherein a stack of materials covers and laterally surrounds the first, second, and third nanosheets of the NFET.