Experimental Investigation of Optimum Gate Workfunction for CMOS Four-Terminal Multigate MOSFETs (MUGFETs)

This paper describes a comprehensive study on the optimum gate workfunction (GWF) for four-terminal-driven multigate MOSFETs (4T-MUGFETs). CMOS 4T-MUGFETs with HfO
₂
high-kappa gate insulator (EOT=1.4 nm) and TiN metal gate have been experimentally demonstrated, and their optimum GWF has been thoroughly investigated. Based on the investigation, it was concluded that the optimum GWF is around 4.32 eV for the NMOS 4T-MUGFETs while 5.17 eV for PMOS 4T-MUGFETs. The reason for the existence of the optimum GWF for the 4T-MUGFETs has been comprehensively explained on the basis of the universal relationship between the initial Vth in the 3T-mode (V
_thDG
), V
_th
in the 4T-mode (V
_th(G1)
), and the second gate bias in the 4T-mode (V
_g2
)