Abstract: An acoustic wave device includes: a substrate; a lower electrode, an air gap being interposed between the lower electrode and the substrate; a piezoelectric film located on the lower electrode; and an upper electrode located on the piezoelectric film such that a resonance region where at least a part of the piezoelectric film is interposed between the upper electrode and the lower electrode is formed and the resonance region overlaps with the air gap in plan view, wherein a surface facing the substrate across the air gap of the lower electrode in a center region of the resonance region is positioned lower than a surface closer to the piezoelectric film of the substrate in an outside of the air gap in plan view.

Abstract: An acoustic wave device includes: first and second terminals located on a first surface of a first substrate; a third terminal that is located on the first surface and is a ground terminal; series resonators located on a second surface of the first substrate and electrically connected in series with a path between the first and second terminals; a parallel resonator that is located on the second surface and has a first end electrically connected to the path and a second end electrically connected to the third terminal; and a fourth terminal located on the first surface, at least a part of the fourth terminal overlapping with, in a thickness direction of the first substrate, at least one of one or more first series resonators of the series resonators, the one or more first series resonators having both ends to which other series resonators are electrically connected.

Abstract: An acoustic wave device includes: a substrate; a lower electrode, an air gap being interposed between the lower electrode and the substrate; a piezoelectric film located on the lower electrode; and an upper electrode located on the piezoelectric film such that a resonance region where at least a part of the piezoelectric film is interposed between the upper electrode and the lower electrode is formed and the resonance region overlaps with the air gap in plan view, wherein a surface facing the substrate across the air gap of the lower electrode in a center region of the resonance region is positioned lower than a surface closer to the piezoelectric film of the substrate in an outside of the air gap in plan view.

Abstract: An acoustic wave device includes: first and second terminals located on a first surface of a first substrate; a third terminal that is located on the first surface and is a ground terminal; series resonators located on a second surface of the first substrate and electrically connected in series with a path between the first and second terminals; a parallel resonator that is located on the second surface and has a first end electrically connected to the path and a second end electrically connected to the third terminal; and a fourth terminal located on the first surface, at least a part of the fourth terminal overlapping with, in a thickness direction of the first substrate, at least one of one or more first series resonators of the series resonators, the one or more first series resonators having both ends to which other series resonators are electrically connected.