The oriented growth of the interfacial PtSi layer between Pt and Si is described. Sputtered Pt onto the (111) Si wafer reacts with Si above 600°C to form PtSi. The interfacial PtSi has the preferred orientation characteristic of the temperature of heat treatment, varying the orientation from [101] at 600°C and 700°C, through [121] at 750°C, to [001] at 800°C. A possible growth mechanism of the interfacial PtSi is proposed on the basis of the atomic layer sequence of each crystallographic direction.