Impact of Non-Rectangular Cross-Section on Electrical Performances of GAA FETs

We investigate the short-channel immunity of various cross-section gate-all-around (GAA) field-effect transistors (FETs): Square (Sq), Rectangular (Re), Trapezoidal (Tz), Circular (Cr), Elliptical (Ep), and triangular with rounded corners (Tr) in terms of above-threshold inversion electron charge density, drain induced barrier lowering (DIBL), subthreshold swing (SS) degradation, gate capacitance (C
gg
), threshold voltage roll-off, and ON-by-OFF ratio. These cross-sections are obtained by varying one or the other key parameters viz. Fin top width (W
top
), Fin height (H
Fin
), inclination angle ($\theta$), and radius of curvature (R). The impact on electrical performances of these parameters as dictated by the processing technology has been analyzed. It is observed that at channel length, $L_{G}=20nm$ the trapezoidal GAA (TzGAA) FET offers 30% reduction in DIBL, 6.4% less degradation in SS, 57% reduction in threshold voltage roll-off, and 22% higher gate capacitance compared to the rectangular counterpart if their bottom widths are equal. Despite ReGAA FET has slightly higher C
gg
compared to EpGAA, the later shows enhanced immunity to short-channel effects. The electron density of TzGAA FET has been observed to decrease with an increase in $\theta,\ H_{Fin},\ W_{top}$, and R. Besides, we calculated the analoyRF parameter dependence on $\theta$ of TzGAA FET. We believe our findings could represent guidelines for the design of high-performance GAA FETs.