Reduction of parasitic bipolar transistor action and punchthrough susceptibility in MOSFETs using Si/Si1-xGex sources and drains

Silicon CMOS devices are subject to some limitations as the dimensions are scaled down for VLSI applications. The incorporation of SiGe into the p-channel device can reduce parasitic bipolar action and punchthrough susceptibility. The authors compare the properties of elevated source and drain devices with and without Si_1-xGe _x in the source and drain regions. We show that the parasitic bipolar gain is reduced by a factor of 18 and that the punchthrough effects seen in silicon devices are absent in the Si_0.8Ge_0.2 devices