Schottky barrier diodes are fabricated on silicon surfaces whose impurity concentrations are controlled by ion implantation techniques. The barriers are produced by PtSi or Al-Si. The forward characteristics of the diodes show that the forward voltages of Schottky barrier diodes made by PtSi are lower than those made by Al-Si for implanted doses of 2×1013 cm−2 and higher. Spreading resistance measurements show that the implanted phosphorus atoms are piled up near the PtSi-Si interface during PtSi formation. This phenomenon causes reduction of the effective barrier height.