Study of Work-Function Variation in High- $\kappa $ /Metal-Gate Gate-All-Around Nanowire MOSFET

In this paper, threshold-voltage (V
_TH
) variation caused by work-function variation (WFV) in a high-κ/metalgate gate-all-around (GAA) nanowire MOSFET is quantitatively estimated through 3-D technology computer-aided design simulations. It is determined that the ratio of average grain size to gate area (RGG) [i.e., RGG = G
_size,eff
/(gate area)
^0.5
] for the GAA nanowire MOSFET should use the effective grain size (G
_size,eff
), instead of using the nominal grain size (G
_size
). G
_size,eff
is regarded as the effective grain size around the channel region, and it is smaller than the original grain size. In order to compare the WFV-induced VTii variation in GAA nanowire MOSFET against FinFET, the amount of WFV-induced V
_TH
variation is plotted using the RGG concept with G
_size,eff
. As a result, it was concluded that the cylinder-shaped GAA nanowire MOSFET has better immunity to the WFV-induced V
_TH
variation by 12.5%, compared with FinFET.