Acoustic wave device with spinel layer

A radio frequency module comprising:

• an acoustic wave filter configured to filter a radio frequency signal, the acoustic wave filter including an acoustic wave device configured to generate an acoustic wave having a wave length of λ, the acoustic wave device including a piezoelectric layer having a thickness of less than λ, an interdigital transducer electrode on the piezoelectric layer, and a polycrystalline spinel layer arranged such that the piezoelectric layer is disposed between the polycrystalline spinel layer and the interdigital transducer electrode;
• and
• a package enclosing the acoustic wave filter.

A wireless communication device comprising:

• an antenna;
• and
• an acoustic wave filter in communication with the antenna, the acoustic wave filter being configured to filter a radio frequency signal, the acoustic wave filter including an acoustic wave device configured to generate an acoustic wave having a wave length of λ, the acoustic wave device including a piezoelectric layer having a thickness of less than λ, an interdigital transducer electrode on the piezoelectric layer, and a polycrystalline spinel layer arranged such that the piezoelectric layer is disposed between the polycrystalline spinel layer and the interdigital transducer electrode.