A novel ultrathin vertical channel NMOSFET with asymmetric fully overlapped LDD

In this letter, a novel ultrathin vertical channel (UTVC) NMOSFET with asymmetric fully overlapped lightly doped drain (LDD) is proposed and demonstrated using solid-phase epitaxy (SPE). A boron-doped polycrystalline Si/sub 0.5/Ge/sub 0.5/ gate was used to tune the threshold voltage, a lightly doped (<1/spl times/10/sup 15/ cm/sup -3/) channel was used to suppress the electron mobility degradation, and an asymmetric fully overlapped LDD was adopted to reduce the series resistance as compared to the conventional LDD. Devices with 50-nm channel length were achieved by using 15-nm ultrathin channel thickness, and they provided high current drive, steep subthreshold slope, and good V/sub T/ roll-off characteristics.