The frequency switchable filters are suitable for selecting the vacant frequency bands. Usual polarity unidirectional single-layered resonators excite 1st mode whereas polarity inverted two-layered resonators excite 2nd mode. We previous reported the frequency switchable two-layered PZT/PbTiO3 epitaxial film resonators. However, PbTiO3 films grown on PZT/PbTiO3 films are difficult to obtain since Curie temperature and deposition temperature in PbTiO3 are higher than those of PZT. (Bax, Sr1-x)TiO3 (BST) films exhibit electrostrictive effect in paraelectric phase. In ferroelectric BaTiO3, on the other hand, polarity inversion is impossible to be obtained without the application of higher than coercive electric field to films. Therefore, in this study, we considered that polarity inverted structure is easily obtained by application of less than coercive electric field of BaTiO3 to two-layered BaTiO3/BST epitaxial films. T. Mori, et al., Proc. IUS 2016.