We report the concept and demonstration of a nanoscale ultra-thin-body silicon-on-insulator (SOI) P-channel MOSFET with a Si1-xGex/Si heterostructure channel. First, a novel lateral solid-phase epitaxy process is employed to form an ultra-thin-body that suppresses the short-channel effects. Negligible threshold voltage roll-off is observed down to a channel length of 50 nm. Second, a selective silicon implant that breaks up the interfacial oxide is shown to facilitate unilateral crystallization to form a single crystalline channel. Third, the incorporation of SiGe in the channel resulted in a 70% enhancement in the drive current.