Through fabricating Ni-FUSI metal gate capacitors and analyzing their C-V and Vfb-EOT characteristics, it is found that Ga or Yb has more favorable modulation ability than conventional dopants. The work function of Ni-FUSI metal gate is modulated close to the top of valince band and the bottom of conduction band, which meets the requirement of high performance CMOS devices. The high modulation abilities of Ga and Yb are explained by dipole theory. Moreover, it is found that the capacitance value of Ni-FUSI metal gate capacitor increases after incorporating Ga or Yb into Ni-FUSI metal gate, but the gate leakage current decreases. And the detailed explanation for the above phenomena is also included in this article by analyzing C-V and gate leakage current characteristics.