Bandgap engineering in vertical P-MOSFETs

Bandgap engineering in vertical P-MOSFETs has been investigated in view of suppressing the short channel effects, floating body effect, and improving the drive current. SiGe source heterojunction P-MOSFETs have been used to s uppress the short channel effects for sub-100 nm devices. While the leakage is reduced, the drive current is also reduced due to the use of a heteroju nction. In this paper, we discuss a SiGe source heterojunction vertical P-M OSFET with a few nanometers thick Si cap. With this device structure, the a bsence of the heterojunction-induced potential barrier right below the oxid e interface improves the drive current substantially while the drain induce d barrier lowering effect and floating body effect are still suppressed. To further improve the drive current of the device, a SiGe/Si cap was added t o the SiGe heterojunction P-MOSFET. We call this device a high mobility het erojunction MOSFET (HMHJT). Compared with the Si control device, the HMHJT has higher drive current and less off-state current at the same time. (C) 2 001 Published by Elsevier Science Ltd.