Observed Off-State Leakage Reduction and Threshold Modulation in Body-Contacted Vertical-Channel FETs

Using the newly developed integrated process, n-type body-contacted vertical-channel FETs (BC-VFETs) were successfully fabricated, achieving low off leakage and wide threshold-voltage adjustability. It was confirmed that the body-contact position, length of upper/lower gate could be accurately controlled by epitaxial growth, which are crucial for massive manufacturing. The horizontal p+body is formed by the dopant diffusion in epitaxial doped side layer. The metal gate etch-back minimizes parasitic gate-drain capacitances. In transfer measurements, applying a grounded body bias reduces minimum off-state current (Imin) to 73% of the floating-body value, while a –0.5 V bias further suppresses it to 44%. AVtshift of –0.38 V/V is also achieved asVBis swept from –1 V to 0 V. Four-terminal analysis confirms that gate-induced drain leakage (GIDL) dominates the deep off-state, while e-BTBT at the body depletion boundary overtakes the body-bias-induced suppression of channel off-state leakage under deep negative body bias, introducing a fundamental trade-off to theVBsetting. With further scaling, this architecture offers a viable path toward 4F2DRAM integration.