Characteristics of Schottky barriers formed on homoepitaxial diamond film have been studied. Current–voltage characteristics of Al contacts on both the as‐grown film and the oxidized film show rectification. On the other hand, ohmic property is observed on Au/as‐grown film while Au/oxidized film shows rectification. These results imply that the mechanism of the barrier formation on the as‐grown diamond is drastically changed by oxidation. The difference of electrical properties between the as‐grown film and the oxidized film is also observed from capacitance–voltage characteristics. This result suggests that additional acceptors which are not related to boron, exist in the as‐grown film and disappear after oxidation. ©1995 American Institute of Physics.