Acoustic wave device

An acoustic wave device comprising:

• a substrate;
• an acoustic reflection layer located in or on the substrate, the acoustic reflection layer including an air gap, or an acoustic mirror in which at least two layers with different acoustic characteristics are stacked;
• a piezoelectric film located on the substrate and the acoustic reflection layer;
• a lower electrode and an upper electrode located on the substrate and the acoustic reflection layer so as to sandwich the piezoelectric film so that a plurality of resonance regions are located within the acoustic reflection layer in plan view so as to share the acoustic reflection layer, one of the lower electrode and the upper electrode being divided, another one of the lower electrode and the upper electrode being not divided, the lower electrode and the upper electrode facing each other across at least a part of the piezoelectric film in each of the plurality of resonance regions;
• and
• an insertion film located between the lower electrode and the upper electrode and located in at least a part of an outer peripheral region of each of the plurality of resonance regions in plan view, the insertion film being not located in a center region of each of the plurality of resonance regions.