Complicated Subthreshold Behavior of Undoped Cylindrical Surrounding-Gate MOSFETs

This paper studied the complication of sub-threshold slope and threshold voltage of undoped Surrounding-Gate (SRG) MOSFETs based on a rigorous classical channel potential model. The detail theoretical analysis demonstrates that the sub-threshold behavior of SRG MOSFETs strongly depends on the silicon body radius. The ideal sub-threshold slope factor S = 60 mV/Dec only appears when the body radius is smaller than a critical value. With a larger silicon body radius, a dual sub-threshold slope factor is displayed. The complex sub-threshold behavior of SRG MOSFETs complicates the definition and extraction of the threshold voltage, which has also been studied in this paper.