The early stage of silicide formation was studied by depositing Si on W tip specimens of the FIM and the atom probe. The optimum temperature for W silicide formation was found to be 900–1000 K and its composition was WSi2. The observed FIM image of the silicide agreed well with the computer‐simulated image which was composed of the W atoms of the tetragonalC11bstructure. The silicide often grew independently on each W{001} plane because the W lattice constant of these planes matches well with that of the basal plane of the silicide. The boundary between the independently grown silicides was also observed along the expected areas from the simulated image.