As the scaling of silicon (Si) CMOS device continues, new materials such as SiGe, Ge, group III-V semiconductor, CNT, and Graphene are introduced due to the limit of Si CMOS such as short channel effects (SCE) and mobility degradation. Ge metal oxide semiconductor field effect transistors (Ge-MOSFETs) have received a lot of attention because of their higher carrier mobility compared with Si. Other advantages of Ge are its lower melting point and lower thermal budget processes compared with Si. However, Ge technology also has disadvantage. Currently, Ge MOSFET devices face several challenges such as water solubility, poor stability of germanium oxides, and small band gap [1-2]. The smaller band gap of Ge leads to higher off-current in MOSFET due to its higher source/drain junction leakage and worse SCE.