The effect of the Si 1− x Ge x source with an underlying p + region on the suppression of the floating body effects in a partially depleted silicon-on-insulator (SOI) metal oxide silicon field effect transistor (MOSFET) is numerically investigated. Compared to a conventional SOI MOSFET, the kink effect and anomalous sub-threshold slope are reduced and the breakdown voltage is substantially increased. The detailed suppression mechanism is also studied. Our results suggest that the narrow bandgap Si 1− x Ge x source and buried p + region are favorable to the dispersion of holes generated by impact ionization.