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. Vt can be modulated through workfunction metal (WFM) thickness as well as the inter-nanosheet spacing (Tsus), the combination of which may be leveraged to increase the number of undoped Vt offerings within a CMOS device menu relative to a FinFET CMOS device menu, which fundamentally does not have Tsus as a Vt tuning option. Hence we propose our multi-Vt scheme by taking advantage of the unique structure of stacked GAA transistor.