A structure and method of fabrication for MOSFET devices with a polycrystalline SiGe junction is disclosed. Ge is selectively grown on Si while Si is selectively grown on Ge. Alternating depositions of Ge and Si layers yield the SiGe junction. The deposited layers are doped, and subsequently the dopants outdiffused into the device body. A thin porous oxide layer between the polycrystalline Ge and Si layers enhances the isotropy of the SiGe junctions.