CaF2 polycrystalline films were treated with a Lewis acid to form a space charge layer of F--vacancies at the adsorbed interface. After the adsorption of SbF5 molecules on the film, the impedance spectra changed from one semicircle to two semicircles. Investigation of these impedance results, combined with the equivalent circuit models, suggest that the high-frequency semicircle may be ascribed to the high conduction layer connected in parallel with bulk conduction and the low frequency semicircle suggests the blocking effect of a perpendicular barrier for the current flow. Numerical estimation is reasonably consistent with this model. This confirms that space charge layers composed of ion vacancies can be systematically created using the chemical attractive force of Lewis acids.