Demonstration of Asymmetric Gate-Oxide Thickness Four-Terminal FinFETs Having Flexible Threshold Voltage and Good Subthreshold Slope

Flexibly controllable threshold-voltage (V
_th
) asymmetric gate-oxide thickness (T
_ox
) four-terminal (4T) FinFETs with HfO
₂
[equivalentoxidethickness(EOT)=1.4 nm] for the drive gate and HfO
₂
+thick SiO
₂
(EOT=6.4-9.4 nm) for the V
_th
-control gate have been successfully fabricated by utilizing ion-bombardment-enhanced etching process. Owing to the slightly thick V
_th
-control gate oxide, the subthreshold slope (S) is significantly improved as compared to the symmetrically thin T
_ox
4T-FinFETs. As a result, the asymmetric T
_ox
4T-FinFETs gain higher I
_on
than that for the symmetrically thin T
_ox
4T-FinFETs under the same I
_off
conditions