The valence band offsets at the heterointerfaces of the CdF2/CaF2/Si(111) structure grown by molecular beam epitaxy were evaluated using x‐ray photoelectron spectroscopy, and the energy band diagram of this heterostructure was proposed. It was found that the interface of CdF2/CaF2has large conduction band offset: 2.9 eV, and the energy level of CdF2conduction band edge is below that of Si. ©1995 American Institute of Physics.