The change in electronic structure from a typeAto a typeBNiSi2/Si(111) interface is sufficient to explain the previously observed difference in the Schottky barrier heights of these two interfaces. This is supported by the observation by scanning tunneling microscopy of different contrast on the faulted triangle in a Si(111) 7×7 unit cell relative to the unfaulted one. The crystallographic differences in the two types of NiSi2/Si(111) interfaces are identical to those in two types of triangles inside a Si(111) 7×7 unit cell. A simple model with an interface dipole induced by the stacking fault is proposed to be responsible for the 0.13 eV difference in the Schottky barriers at typeBNiSi2/Si(111) interfaces relative to typeAinterfaces. The estimated dipole change is about 0.004e−per interface bond, in good agreement with a theoretical estimation at the stacking fault of bulk Si.