Device and Circuit Performance Estimation of Junctionless Bulk FinFETs

The design and characteristics of junctionless (JL) bulk FinFET devices and circuits are compared with the conventional inversion-mode (IM) bulk FinFET using 3-D quantum transport device simulation. The JL bulk FinFET shows better short channel characteristics, including drain-induced barrier lowering, subthreshold slope, and threshold voltage (
V
_th
) roll-off characteristics at supply voltage (
V
_DD
) 1 V. Analyses of electron density and electricfield distributions in on-state and off-state also show that the JL devices have better on-off current ratios. Regarding design aspects, the effects of channel doping concentration (
N
_ch
) and Fin height (
H
)/width (
W
) on device
V
_th
are also compared. In addition, the
V
_th
of the proposed JL bulk FinFET can be easily tuned by an additional parameter, substrate doping concentration (
N
_sub
). Inverter performance and static random access memory (SRAM) circuit performance are also compared using a coupled device-circuit simulation. The high-to-low delay time (
t
_HL
) and low-to-high delay time (
t
_LH
) of the inverter with JL bulk FinFET are smaller than the inverter with IM bulk FinFET. The JL bulk FinFET SRAM cell also provides a similar static transfer characteristic to those of IM bulk FinFET SRAM cell, which show large potential in digital circuit application.