We have studied the effect of the interface between tungsten silicide and polysilicon the silicide reaction. The results showed that the cleaning of the silicon surface prior to the deposition of tungsten silicide affected the interface properties, thereby leading to the difference in the resistivity and surface morhpology of tungsten silicide. Compared with HF cleaning, the use of SCl cleaning yielded higher resistivity of tungsten silicide at the low anneal temperature (up to $900^{circ}C$). However, furtherature to $1000^{circ}C$ reduced the resistivity significantly, similar to that obtained with HF cleaning. It was also observed that the annealing of WSix/HF-cleaned poly-si allowed the formation of bucking weve (partially decohesion area) on the surface. In contrast, the use of SCl celaning did not produce the buckling waves on the surface. Also the presence of 200$AA$ -thick TiW between tungsten silicide and HF-cleaned poly-Si effectively prevented the formation of the waves. However, high-temperature annealing of WSix/200A-TiW/Poly-Si allowed the excess silicon in tungsten silicide to precipitate inside the silcide, causing the slight increase of the resistivity after annealing at $1050^{circ}C$