The resonance apparatus 400 includes the reflective layer 404 in addition to the elements of the resonance apparatus 100 of FIG. 1. Therefore, the same elements as in the resonance apparatus 100 of FIG. 1 will not be described again with reference to FIG. 4 for conciseness.

The reflective layer 404 is formed on an upper portion of the substrate 401, and in a partial region of the cavity 403 formed at the upper portion of the substrate 401. As shown in FIG. 4, a side of the reflective layer 404 contacts the lower electrode 402, while another side of the reflective layer 404 contacts the piezoelectric layer 405. The reflective layer 404 reflects the acoustic wave converted in the piezoelectric layer 405.

The reflective layer 404 includes a first reflective layer 409 and a second reflective layer 410. The first reflective layer 409 is formed on an upper portion of the second reflective layer 410. The cavity 403 is formed at an upper portion of the first reflective layer 409. The first reflective layer 409 includes a relatively lower acoustic impedance than the second reflective layer 410. For example, the first reflective layer 409 may be made of a silicon oxide (SiO) based material, a SiN-based material, and/or an aluminum oxide (AlO) based material.