This paper investigates the effects of ion implantation and spike activation anneal on the work function (WF) modulation of Ni fully silicided (FUSI) metal gate on SiO2 dielectrics, and on the FUSI gated SiO2/ Si(1 0 0) interface trap properties by using high-frequency capacitance-voltage (C-V) and photonic high-frequency C-V measurements. Undoped Ni FUSI gate has good thermal stability, and its WF before and after forming gas annealing (FGA) is 4.75 eV and 4.74 eV, respectively. As pre-doping and B pre-doping shift the. atband voltage of the Ni FUSI gated MOS capacitor negatively and positively, respectively. As-doped Ni FUSI gate may delaminate or peel off after FGA. Before FGA, a characteristic D-it peak ranging from 5.7 x 10(12) to 1.2 x 10(13) cm (2) eV (1) was observed at approximately 0.63-0.74 eV above the valence band edge for As-doped and B-doped Ni FUSI gated capacitors which received a spike activation anneal after ion implantation. But such a Dit peak was not observed in undoped Ni FUSI gated capacitors or those doped but without a spike activation anneal. The characteristic peak, which may be related to P-b defects at the SiO2/Si(1 0 0) interface, could be eliminated after FGA. (C) 2008 Elsevier B. V. All rights reserved.