A filter includes a first filter circuit and an additional circuit. The first filter circuit includes a resonator electrode and a main wire. The main wire includes first and second metal films, the second metal film being in contact with the first metal film. The additional circuit includes an IDT electrode group including IDT electrodes and a sub-wire connecting the IDT electrode group to the first filter circuit. At least a portion of the sub-wire includes a third metal film connected to the IDT electrode group. The third metal film is covered with a fourth metal film with an insulating layer interposed therebetween, the insulating layer being provided on the third metal film. The fourth metal film is connected to a ground terminal on a substrate.

In an acoustic wave device, a piezoelectric layer is provided directly or indirectly on a support substrate, an IDT electrode is provided on the piezoelectric layer, an overlap region includes a middle region and first and second edge regions, and first and second conductive layers are provided on a second main surface of the piezoelectric layer to overlap at least some portions of the first and second edge regions in plan view and at least some portions of first and second busbars in plan view.

An acoustic wave device includes a high acoustic velocity structure, a low acoustic velocity layer on the high acoustic velocity structure, a piezoelectric layer directly or indirectly on the low acoustic velocity layer, and an electrode on the piezoelectric layer. The low acoustic velocity layer is made of a dielectric material having a lower Young's modulus than silicon oxide, or includes the dielectric material as a main component.

A bandpass acoustic wave filter device includes an IDT electrode and a dielectric film disposed on a piezoelectric substrate including a LiNbO.sub.3 layer, and an acoustic wave resonator is defined by the IDT electrode. The acoustic wave resonator utilizes the Rayleigh wave, and a response of an SH wave excited by the acoustic wave resonator is outside a pass band of the acoustic wave filter device.

An acoustic wave element includes an IDT electrode including electrode fingers, a first substrate on an upper surface of which the IDT electrode is located, which has a thickness of less than 2 times a repetition interval of the electrode fingers and is configured by a piezoelectric crystal, a second substrate bonded to a lower surface of the first substrate, and configured by an Si single crystal having a plane orientation of a (100) plane or (110) plane or a plane equal to them, in which substrate a crystal axis of the Si single crystal parallel to a substrate surface of Si single crystal is inclined at any angle of 25° to 65°, 115° to 155°, 205° to 245°, and 295° to 345° relative to a direction of propagation of an acoustic wave when viewed from the upper surface of the superposed first substrate.

A surface acoustic wave (SAW) resonator comprises a plurality of interdigital transducer (IDT) electrodes disposed on a multilayer piezoelectric substrate including a layer of piezoelectric material having a lower surface bonded to an upper surface of a layer of a dielectric material. The dielectric material has a lower surface bonded to an upper surface of a carrier substrate. The plurality of IDT electrodes include an upper layer and a lower layer. The upper layer is formed of a material having a higher conductivity than the lower layer. The lower layer is formed of a material having a higher density than the upper layer to provide for reduction in size of the SAW resonator.

An acoustic wave device includes a semiconductor substrate having a first main surface and a second main surface, a piezoelectric thin film provided directly on or indirectly above the first main surface of the semiconductor substrate, and an IDT electrode provided on the piezoelectric thin film. A semiconductor defining the semiconductor substrate is a high acoustic velocity material in which an acoustic velocity of a bulk wave propagating therethrough is higher than an acoustic velocity of an acoustic wave propagating through the piezoelectric thin film. The semiconductor substrate includes a first region including the first main surface and a second region which is a region other than the first region and includes the second main surface. An electric resistance of the first region is lower than an electric resistance of the second region.

A filter device includes resonators including at least one series arm resonator and at least one parallel arm resonator. The resonators include a parallel arm resonator defining and functioning as a first resonator with a largest fractional bandwidth among the resonators, and at least one second resonator. The filter device includes an inductor connected in series to the first resonator.

The present disclosure provides an acoustic resonator device, among other things. One example of the disclosed acoustic resonator device includes a substrate having a carrier layer, a first layer disposed over the carrier layer, and a piezoelectric layer disposed over the first layer. The acoustic resonator device is also disclosed to include an interdigitated metal disposed over the piezoelectric layer, where the interdigitated metal is configured to generate acoustic waves within an acoustically active region. The acoustic resonator device is further disclosed to include an acoustic wave scattering structure.

An elastic wave device includes a piezoelectric layer, an IDT electrode on the piezoelectric layer, a high-acoustic-velocity member, a low-acoustic-velocity film between the high-acoustic-velocity member and the piezoelectric layer. The piezoelectric layer is made of lithium tantalate, the IDT electrode includes metal layers including an Al metal layer and a metal layer having a higher density than Al. Expression 1 is satisfied: 301.74667−10.83029×T.sub.LT−3.52155×T.sub.ELE+0.10788×T.sub.LT.sup.2+0.01003×T.sub.ELE.sup.2+0.03989×T.sub.LT×T.sub.ELE≥0 expression 1, where λ represents a wavelength defined by an electrode finger pitch of the IDT electrode, T.sub.LT (%) represents a normalized film thickness of the piezoelectric layer to the wavelength λ, and T.sub.ELE (%) represents a normalized film thickness of the IDT electrode in terms of Al to the wavelength λ.