The formation of PtSi is studied in the presence of W and Al using the Al/W/Pt/Si structure, with 1000-Å W acting as the barrier layer. The PtSi layer formed stays intact at 400 °C, starts to react with Al around 450 °C, and is completely converted to PtAl2 at 500 °C, with the released Si migrating to the surface. In contrast, using the W/Pt/Si structure without an Al layer, the PtSi formed remains little changed up to about 600 °C. The W-Pt interface of the binary W/Pt structure shows no interaction up to at least 600 °C. The results are compared with those using the Al/Pt/Si structure, and their relation to contact metallurgies is discussed.