A silicide method was for the first time studied to improve the thermal stability of nickel monosilicide by adding a thin W interlayer within the nickel film. The results show that after rapid thermal annealing (RTA) at temperatures ranging from 650 °C to 800 °C, the sheet resistance of formed Ni(W)Si samples was lower than that of nickel monosilicide without the interlayer. X-ray diffraction (XRD) and raman spectra results both reveal that only the NiSi phase exists in these samples, but the high resistance NiSi2 phase does not. According to the Gibbs free energy theory, the incorporation of a 7.3 atomic ratio of the W element in the ternary silicide can delay the appearance of the high resistivity NiSi2 phase, and thus enhance the thermal stability of the NiSi film. Fabricated Ni(W)Si/Si Schottky barrier diodes displayed good quality, with the barrier height being located generally between 0.64 eV and 0.66 eV and the ideality factor approaching unity. This further shows that the presence of the W interlayer in nickel silicide is effective in promoting the thermal stability and electrical characteristics of nickel monosilicide.