Vertical P-MOSFETs with heterojunction between source/drain and channel

The growth of high quality strained SiGe-Si and SiGeC-Si heterostructures allows incorporation of band gap engineering into Si technology, which can be used to improve device characteristics. A heterojunction MOSFET (HJMOSFET) structure has been proposed in which the large valence band offset at SiGe-Si heterojunctions reduces the punchthrough and DIBL for P-MOSFETs (Hareland et al, 1993). Vertical MOSFETs allow more freedom in terms of band gap engineering, and the channel length is not limited by the lithography (Liu et al, 1998). In this paper, we show experimentally that the heterojunction at the source can be used to suppress the floating body effect and short channel effect. Vertical P-MOSFETs with strained SiGe and SiGeC sources have been fabricated with 60-75 nm effective channel lengths. The electrical characteristics of the devices are compared with those of control Si devices and with simulation results.