An acoustic wave device includes a high-acoustic-velocity layer, a piezoelectric layer made of lithium tantalate, and an interdigital transducer electrode that are successively laminated. An acoustic velocity of a bulk wave propagating in the high-acoustic-velocity layer is higher than an acoustic velocity of an acoustic wave propagating in the piezoelectric layer, and an acoustic velocity Vsub of a fast transversal bulk wave propagating in the high-acoustic-velocity layer satisfies Vsh0VsubVsp with respect to an acoustic velocity Vsh0 of an SH0 mode and an acoustic velocity Vsp of a mode becoming a spurious of which acoustic velocity is not lower than the acoustic velocity of the SH0 mode, wherein the acoustic velocity Vsh0 and the acoustic velocity Vsp is obtained from Eq. (1).

A composite substrate 10 includes a first substrate 10 comprised of a piezoelectric single crystal and a second substrate 20 comprised of a silicon single crystal bonded to the first substrate 10. In the second substrate, a planar orientation is (111), and of Euler angles (, , ) is offset from 0. Due to this, a bulk wave spurious is reduced in a specific frequency band.

An acoustic resonator includes a substrate, and a resonant portion comprising a center portion in which a first electrode, a piezoelectric layer and a second electrode are sequentially laminated on the substrate, and an extending portion disposed along a periphery of the center portion, wherein the resonant portion is configured to have an asymmetrical polygonal plane, an insertion layer is disposed below the piezoelectric layer in the extending portion, and the piezoelectric layer is configured to have a top surface which is raised to conform to a shape of the insertion layer, and the insertion layer is configured to have an asymmetrical polygonal shape corresponding to a shape of the extending portion.

A transducer includes first and second piezoelectric layers made of corresponding different first and second piezoelectric materials and three or more electrodes, implemented in two or more conductive electrode layers. The first piezoelectric layer is sandwiched between a first pair of electrodes and the second piezoelectric layer is sandwiched between a second pair of electrodes. The first and second pairs of electrodes contain no more than one electrode that is common to both pairs.

A piezoelectric element body has a first principal surface and a second principal surface. A pair of first electrodes is disposed on the first principal surface. The vibrating body includes a metal plate, an insulating layer, and a pair of second electrodes. The metal plate has a third principal surface and a fourth principal surface. The insulating layer is disposed on the third principal surface. The pair of second electrodes is disposed on the insulating layer. The piezoelectric element and the vibrating body are disposed in such a manner that the first principal surface and the third principal surface oppose each other via the insulating layer. The pair of second electrodes physically contacts the respective first electrodes. The second electrodes are exposed from the piezoelectric element and are separated from all of edges of the insulating layer, when viewed from a direction orthogonal to the third principal surface.

An acoustic resonator includes a substrate, an insulation layer disposed on the substrate, a resonating portion disposed on the insulation layer and having a first electrode, a piezoelectric layer, and a second electrode, stacked thereon, a cavity disposed between the insulation layer and the resonating portion, a protruded portion having a plurality of protrusions disposed on a lower surface of the cavity, and a hydrophobic layer disposed on an upper surface of the cavity and a surface of the protruded portion.

A resonance device is provided having a resonator with opposing upper and lower lids. The resonator includes a base, and multiple vibration arms that are connected to a front end of the base so as to extend away from the base. Moreover, a frame surrounds a periphery of the base portion and the vibration arms and one or more holding arms connect the base to the frame. The base, the vibration arms, and the holding arm include a substrate and a temperature characteristics correction layer laminated on the substrate and having a material with a coefficient of thermal expansion different from that of the substrate. The base, the vibration arms, and the holding arm are formed integrally with the substrate and the temperature characteristics correction layer.

A transducer includes first and second piezoelectric layers made of corresponding different first and second piezoelectric materials and three or more electrodes, implemented in two or more conductive electrode layers. The first piezoelectric layer is sandwiched between a first pair of electrodes and the second piezoelectric layer is sandwiched between a second pair of electrodes. The first and second pairs of electrodes contain no more than one electrode that is common to both pairs.

A piezoelectric thin film resonator includes: a substrate; lower and upper electrodes located on the substrate; a piezoelectric film that has a lower piezoelectric film mainly composed of aluminum nitride and an upper piezoelectric film mainly composed of aluminum nitride, the lower piezoelectric film and the upper piezoelectric film being in contact with each other in at least a part of a resonance region where the lower electrode and the upper electrode face each other across at least a part of the piezoelectric film, and a fluorine concentration at a boundary face with which the lower piezoelectric film and the upper piezoelectric film are in contact being 0.03 atomic % or less; and an insulating film that is located between the lower piezoelectric film and the upper piezoelectric film in a region other than the at least a part of the resonance region and contains silicon oxide.

An acoustic resonator includes a substrate, and a resonant portion comprising a center portion in which a first electrode, a piezoelectric layer and a second electrode are sequentially laminated on the substrate, and an extending portion disposed along a periphery of the center portion, wherein the resonant portion is configured to have an asymmetrical polygonal plane, an insertion layer is disposed below the piezoelectric layer in the extending portion, and the piezoelectric layer is configured to have a top surface which is raised to conform to a shape of the insertion layer, and the insertion layer is configured to have an asymmetrical polygonal shape corresponding to a shape of the extending portion.