Electric field penetration into the metallic side of a Schottky junction is in principle a universal phenomenon, the magnitude of which increases with the semiconductor permittivity. Here, we quantitatively probe this effect using bias-dependent internal photoemission spectroscopy at the Schottky junction between a large dielectric permittivity semiconductor SrTiO3 and gold. A clear linear reduction of the barrier height with increasing interface electric field was observed, highlighting the importance of field penetration into the gold. The interfacial permittivity of SrTiO3 at the interface is reduced from the bulk value, reflecting intrinsic suppression at the interface. Show Partial Abstract