We have observed temperature-dependent reversal of the rectifying polarity in Au/ Nb: SrTiO 3 Schottky junctions. By simulating current-voltage characteristics, we have found that the permittivity of SrTiO 3 near the interface exhibits temperature dependence opposite to that observed in the bulk, significantly reducing the barrier width. At low temperature, tunneling current dominates the junction transport due both to such barrier narrowing and to suppressed thermal excitations. The present results demonstrate that junction properties can be dominated by the interface permittivity.