The properties of c-oriented thin films Sr0.5Ba0.5Nb2O6 grown on a Si(001) (p-type) substrate with a pre-deposited Ba0.2Sr0.8TiO3 layer were studied using scanning probe microscopy and dielectric spectroscopy. It is established that the films Sr0.5Ba0.5Nb2O6 are characterized by low surface roughness (less than 6 nm), average crystallite size 93 nm. It is shown that there is spontaneous polarization in the film directed from its surface to the substrate, which caused the manifestation of the field effect for the case of the Si substrate with p-type conductivity without external field effect. Differences in the magnitude of the surface potential signal for regions polarized by an external electric field of different polarities (+10 and −10 V), as well as in their relaxation to the initial state, are revealed. The reasons for the established patterns are discussed.