The room‐temperature current‐voltage characteristics for thermally grown Al2O3dielectric films sandwiched between the Al base electrode and the Zn, Sn, or Au counter electrode were studied. Experimentally, voltage ranges were found for which the Schottky mechanism appears to be dependent on the energy band structure of the metal‐insulator‐metal configuration. The film current changes from a logJ‐V½(the Schottky mechanism) dependency to a logJ‐Vdependency at a particular applied voltageVB. Empirically, the sum &phgr;+eVB=&psgr;, where &phgr; is the metal‐insulator barrier, is in agreement with the work function &psgr; of the positive metal electrode. In consideration of thisad hocagreement, the contact potential &psgr;CP=&Dgr;&phgr;+&Dgr;eVB, where &Dgr;&phgr; is the difference (asymmetry) in the calculated metal‐insulator barrier for positive and negative polarities, and &Dgr;eVBis the difference in the voltages for the change of mechanisms for the corresponding polarities. The mechanism by which the film currents change from the Schottky emission to the logJ‐Vdependency at a particular voltageVBis not understood.