Schottky barrier PtSi‐Si diodes formed by ultrahigh vacuum deposition and annealing of 1‐nm‐thick Pt films onn‐ andp‐type (100) Si substrates were characterized by current‐voltage measurements at liquid‐nitrogen temperature. The diodes exhibited nearly ideal characteristics, with barrier heights of 0.914 and 0.197 eV, respectively, for typicaln‐ andp‐type devices. Subsequent annealing in hydrogen increased the barrier height by 0.013 eV for then‐type devices and decreased it by the same amount for thep‐type devices. Vacuum annealing of H2‐annealed devices restored the barrier heights to approximately their initial values. These results can be attributed to the presence of Si interface defects that are passivated by hydrogen incorporation and subsequently reactivated by vacuum annealing to remove the hydrogen.