We have demonstrated effective electron Schottky barrier height (eSBH) reduction of NiGe/Ge contacts using phosphorus ion implantation after germanidation. The eSBH was drastically reduced from 0.62 eV to 0.09 eV under optimum implantation and subsequent annealing conditions. Moreover, systematic studies of NiGe/Ge contacts with various P ion profiles indicated the variation in the eSBH at NiGe/Ge interface. This method allows us to design and control junction characteristics for future Ge-based devices.