Diode characteristics of granular‐metal (GM)/n‐Si interfaces were investigated. The granular metal film (Pd or Pt/SiO2) was deposited by the ion‐beam sputtering technique. The diode characteristics were found to be influenced not only by the metal fraction in GM but also by the GM film thickness. Saturation current densityJsof the diodes under reverse bias condition showed a notable peak at the metal fraction in the range between 0.1 and 0.25, the maximum value being several orders of magnitude greater thanJsof a Pd‐Si Schottky barrier. Assuming that the increase inJsis fully caused by the barrier‐height lowering at the GM/Si interfaces, the amounts of barrier‐height lowerings were found to be 0.18 eV for 150‐A˚‐thick GM films and 0.22 eV for 600‐A˚‐thick GM films. Possible mechanisms for the barrier‐height lowering as well as the reason that the barrier height depends upon the GM films’s thickness were considered.