Acoustic wave device and fabrication method thereof

An acoustic wave device, comprising:

• a first substrate, comprising a first surface and a second surface;
• a plurality of first electrodes disposed on the second surface of the first substrate;
• a second substrate, comprising a third surface and a fourth surface;
• a plurality of second electrodes, disposed on the third surface of the second substrate, wherein the second surface of the first substrate faces the third surface of the second substrate, such that the plurality of first electrodes and the plurality of second electrodes are arranged between the first substrate and the second substrate;
• a first film, disposed between the plurality of first electrodes and the plurality of second electrodes;
• and
• a first side wall, disposed on the second surface of the first substrate and at least partially surrounding the plurality of first electrodes;
• wherein the first film covers on the first side wall;
• and
• wherein the first substrate, the first side wall, and the first film are disposed to form a first cavity and the plurality of first electrodes are disposed within the first cavity.