We demonstrate the characteristics of -Ge/n-Si and -Ge/p-Si heterojunction diodes formed by heteroepitaxial Ge grown on Si leading to high performance and very low leakage current. The ON/OFF current ratio of the -Ge/n-Si and -Ge/p-Si heterojunction was and , respectively. The OFF current density was extremely low at for the -Ge/n-Si formed with different implantation energies of 10–40 KeV and for the -Ge/p-Si with different implantation energies of 20–50 KeV at a reverse bias of , respectively. Both p and n-Ge channel multifin field-effect transistors (FinFETs) were formed by a mesa structure using these -Ge/n-Si and -Ge/p-Si heterojunctions. A high-/metal gate stack was employed. The body-tied Ge multifin FinFET with a fin width of , and the channel length was 150 nm for p-FinFET and of 110 nm for n-FinFET, exhibiting a driving current of 174 at and 102 at , respectively. This is the first experimental demonstration of a body-tied high mobility Ge channel multifin FinFET using a top-down approach.