SiGe/Si vertical PMOSFET device design and fabrication

As channel lengths shrink continuously to smaller dimensions in order to improve performance and packing density, lithography, isolation, power supply and short channel effects have proved to be major limitations. Recently vertical MOSFETs (VMOS), also known as surround gate transistors, or 3-D side-wall transistors have been shown to overcome these process limitations. In this paper, we review the various VMOS technologies and applications and compare the performance of these devices to planar devices. We also present a novel deep submicron vertical SiGe/Si PMOSFET fabricated by Ge implantation. The Ge was implanted in the Si vertical channel to form a strained SiGe layer to increase drive current in P channel devices. PMOS drive current can be increased by about 100% compared to Si control devices. Thus, this technology offers CMOS circuit designers the flexibility to match PMOS and NMOS current drive capabilities, which was previously limited by the difference in electron and hole mobilities in Si.