High-k metal gate fundamental learning and multi-Vt options for stacked nanosheet gate-all-around transistor

In this paper, we report multi-threshold-voltage (multi-Vt) options for stacked Nanosheet gate-all-around (GAA) transistors. V
t
can be modulated through workfunction metal (WFM) thickness as well as the inter-nanosheet spacing (T
sus
), the combination of which may be leveraged to increase the number of undoped V
t
offerings within a CMOS device menu relative to a FinFET CMOS device menu, which fundamentally does not have T
sus
as a V
t
tuning option. Hence we propose our multi-V
t
scheme by taking advantage of the unique structure of stacked GAA transistor.