An elastic wave device includes an interdigital transducer (IDT) electrode in contact with a piezoelectric substrate having a bus bar electrode region including one of a first bus bar electrode and a second bus bar electrode of the IDT electrode, an alternately disposed region where first electrode fingers are alternately disposed with second electrode fingers of the IDT electrode, and an intermediate region including one of the first electrode fingers and the second electrode fingers. A dielectric film is formed in at least part of the intermediate region and in contact with an upper surface of the IDT electrode. The dielectric film includes a medium in which an acoustic velocity of a transverse wave propagating in the dielectric film is lower than an acoustic velocity of a main elastic wave of the alternately disposed region. The dielectric film is not formed in the alternately disposed region.

An elastic wave device includes a piezoelectric substrate, an IDT electrode, and a cover member. The IDT electrode is provided on the piezoelectric substrate. The cover member is provided above the piezoelectric substrate and separate from the IDT electrode. The cover member includes a first cover member and a second cover member. The second cover member is laminated on a side of the first cover member opposite to the piezoelectric substrate. The glass transition point of the first cover member is higher than that of the second cover member.

An elastic wave resonator includes a first, second and third reflectors. The first reflector is between a portion including a first IDT electrode and a third IDT electrode and a portion including a second IDT electrode and a fourth IDT electrode and is shared by the first to fourth IDT electrodes. The second reflector is shared by the first and third IDT electrodes. The third reflector is shared by the second and fourth IDT electrodes. The first and third IDT electrodes share a first common busbar. The second and fourth IDT electrodes share a second common busbar. The first and second common busbars are connected to the first reflector. A first busbar, a second busbar, a third busbar, and a fourth busbar of the respective first to fourth IDT electrodes are electrically connected to each other.

Disclosed is a surface acoustic wave device including a piezoelectric substrate, first and second bus bars formed on the piezoelectric substrate to be opposite each other, a plurality of first inter-digital electrodes that are electrically connected to the first bus bar and extend from the first bus bar toward the second bus bar, and a plurality of second inter-digital electrodes that are electrically connected to the second bus bar and extend from the second bus bar toward the first bus bar, in which the first inter-digital electrodes and the second inter-digital electrodes are alternately arranged.

An acoustic wave element (100) according to certain examples includes a piezoelectric body (130), an interdigital transducer (IDT) electrode (140, 150) disposed above the piezoelectric body (130), and a connection electrode (160) disposed above the piezoelectric body (130) and connected to the IDT electrode (140, 150). A first insulation layer (172) covers the connection electrode (160), and a second insulation layer (174a, 174b) covers the IDT electrode (140, 150). The first insulation layer (172) disposed above the connection electrode (160) has a first thickness T in a direction perpendicular to an upper surface of the piezoelectric body (130) and the second insulation layer (174b) disposed above the IDT electrode (150) has a second thickness K in the direction perpendicular to the upper surface of the piezoelectric body (130). The first thickness T is less than the second thickness K based on FIG. 2C and the relevant description.

An elastic wave device includes a low acoustic velocity film, a piezoelectric film, and an IDT electrode, which are laminated on a high acoustic velocity material. In the IDT electrode, first electrode fingers, or second electrode fingers, or each of the first electrode fingers and the second electrode fingers, includes a wide width portion with a dimension in a width direction larger than a dimension at a center in a length direction and being provided closer to at least one of a side of a proximal end and a side of a distal end than a central region, at least one of a first busbar and a second busbar includes cavities arranged in a busbar length direction, and at least one of the first busbar and the second busbar includes an inner busbar portion which is positioned closer to a side of the first electrode fingers or a side of the second electrode fingers than the cavities are and which extends in the length direction of the first busbar and the second busbar, a central busbar portion that includes the cavities, and an outer busbar portion.

An acoustic wave device includes a piezoelectric substrate and an IDT electrode directly or indirectly disposed on the piezoelectric substrate. The IDT electrode includes first metal layers, a second metal layer disposed on one of the first metal layers, and a third metal layer disposed on the second metal layer. The first, second, and third metal layers include side surfaces, respectively. The side surface includes a first end portion adjacent to the second metal layer. The side surface includes a second end portion adjacent to the second metal layer. In at least a portion of the IDT electrode, a creepage distance stretching from the first end portion to the second end portion via the side surface of the second metal layer is longer than a distance between the first end portion and the second end portion.

A ladder-type surface acoustic wave filter assembly includes a plurality of series resonators formed on a substrate and connected between an input terminal and an output terminal. A first series resonator has a lowest resonance frequency among the plurality of series resonator. A parallel resonator formed on the substrate and connected between the plurality of series resonators and the ground terminal. A dielectric film is coupled to at least one of the plurality of series resonators and has an inverse temperature coefficient of frequency to that of the substrate. A film thickness of the dielectric film in a region where the second series resonator is formed is smaller than a film thickness of the dielectric film in a region where the first series resonator is formed.

A transducer for SAW-type or PSAW-type acoustic waves is proposed in which the dielectric (DK) is applied onto the substrate so that the gap (GP) between the ends of the electrode fingers and the opposite bus electrode is completely filled with said dielectric (DK), but the active area of the transducer, thus transversal overlap area (UB) of the electrode fingers, is not covered by said dielectric.

An acoustic wave filter device includes a piezoelectric layer, a high-acoustic-velocity member, a low-acoustic-velocity film between the high-acoustic-velocity member and the piezoelectric layer, and first and second IDT electrodes on the piezoelectric layer to define acoustic wave resonators. An acoustic wave resonator of a series-arm resonator portion closest to an antenna end and/or an acoustic wave resonator of a parallel-arm resonator portion closest to the antenna end includes the first IDT electrode including first and second electrode fingers, and the remaining acoustic wave resonators include the second IDT electrode including third and fourth electrode fingers. In the first IDT electrode, a central area, first and second low-acoustic-velocity areas, and first and second high-acoustic-velocity areas extend along a direction perpendicular or substantially perpendicular to an acoustic wave propagating direction. First and second envelopes connecting the tips of the third and fourth electrode fingers of the second IDT electrode are inclined.