In an IDT electrode of an acoustic wave element which includes first electrode fingers and second electrode fingers connected to potentials which are different from each other and arranged spaced apart from each other, the first electrode fingers includes first tip parts, and either of the first electrode fingers and the second electrode fingers includes, at a tip area extending along a direction of propagation of an acoustic wave and overlapping with the first tip parts, increase sections in which electrode volumes per unit lengths in a direction of extension of the first electrode fingers and the second electrode fingers are larger in comparison with that of the center area in which the electrode fingers intersect.

In an acoustic wave device, an antenna end resonator electrically closest to a first terminal is a first acoustic wave resonator. In each of the first acoustic wave resonator and a second acoustic wave resonator, a thickness of a piezoelectric layer is equal to or less than about 3.5. A cut angle of the piezoelectric layer of the first acoustic wave resonator is within a range of .sub.B4. The cut angle of the piezoelectric layer of the second acoustic wave resonator has a larger difference from .sub.B () than the cut angle of the piezoelectric layer of the first acoustic wave resonator.

A multiplexer includes a first reception-side filter and a second reception-side filter whose passband has frequencies higher than the first reception-side filter. The first reception-side filter includes a series arm resonator provided on a first path, and parallel arm resonators provided on a path electrically connecting the first path and ground. A direction connecting tips of a plurality of electrode fingers included in each resonator crosses an elastic wave propagating direction at a certain angle. The parallel arm resonator closest to a common connection terminal does not include third electrode fingers, and the other parallel arm resonators include third electrode fingers.

Of a plurality of acoustic wave resonators, the acoustic wave resonator electrically closest to a first terminal is an antenna end resonator, the antenna end resonator is a first acoustic wave resonator and at least one acoustic wave resonator other than the antenna end resonator of the plurality of acoustic wave resonators is a second acoustic wave resonator. An acoustic wave device satisfies a first condition. The first condition is a condition that a high acoustic velocity layer of the first acoustic wave resonator and a high acoustic velocity layer of the second acoustic wave resonator each include a silicon substrate, a surface closer to a piezoelectric layer in the silicon substrate of the first acoustic wave resonator is a plane or a plane, and a surface closer to a piezoelectric layer in the silicon substrate of the second acoustic wave resonator is a plane.

An acoustic wave filter includes a substrate having piezoelectricity, input/output terminals on the substrate, ground terminals on the substrate and separated from each other, and a longitudinally coupled resonator on the substrate and arranged on a path connecting the input/output terminals, in which each of IDT electrodes included in the longitudinally coupled resonator includes a pair of comb-shaped electrodes each of which is provided with a plurality of electrode fingers and a busbar electrode, the other of the pair of the comb-shaped electrodes included in the IDT electrode arranged at a position closest to the input/output terminal is connected to the ground terminal on the substrate, and the other of the pair of comb-shaped electrodes included in each of all the IDT electrodes other than the IDT electrode is connected to the ground terminal on the substrate.

A filter device utilizing surface acoustic waves includes one or more series arm resonators connected to each other along a path between a first input/output terminal and a second input/output terminal, and three or more parallel arm resonators each connected between a connection node provided on the path and ground and defining the pass band of the filter device. Parallel arm resonators having different anti-resonant frequencies from each other are included. Parallel arm resonators among the three or more parallel arm resonators are connected to the same connection node provided along the path. Remaining parallel arm resonators are connected to different connection nodes from the same connection node. The anti-resonant frequencies of the parallel arm resonators connected to the same connection node are identical and are the lowest anti-resonant frequencies among the anti-resonant frequencies of the three or more parallel arm resonators.

A filter includes a LiTaO.sub.3 piezoelectric layer having a cut angle, a high acoustic velocity support substrate, a low acoustic velocity film, and an IDT electrode. A cut angle .sub.B of the piezoelectric layer at which a Rayleigh wave spurious response is locally reduced or minimized is determined from a wavelength of the IDT electrode, a film thickness of the IDT electrode, a specific gravity of the IDT electrode, an electrode duty, a thickness of the piezoelectric layer, and a film thickness of the low acoustic velocity film. The Cut angle of the piezoelectric layer satisfies a relationship of .sub.B4.sub.B+4.

An antenna terminal is connected to a first filter and second filter, which are branched from each other when viewed from the antenna terminal, and are different in passing bands from each other. An individual inductor is connected in series to a branch point from which the first filter is branched to be independent from other filters when viewed from the antenna terminal. And a common inductor is located between a position between the antenna terminal and the branch point and a reference potential and is commonly connected in parallel with respect to the filters. The first filter is higher in frequency of passing band compared with the other filters. A susceptance when viewing the second filter side from the antenna terminal is larger than a susceptance when viewing the first filter side from the antenna terminal at frequencies of passing bands of them.

The present disclosure relates to acoustic wave devices, and particularly to high quality factor (Q) transducers for surface acoustic wave (SAW) devices. An exemplary SAW device includes an interdigital transducer (IDT) between two reflective gratings to form a resonator. The resonator operates through shear horizontal mode acoustic waves, and therefore suppression of transverse modes (parallel to electrode fingers of the IDT) is desired. A piston mode can be formed in the resonator to suppress transverse modes, which may also increase energy leakage and result in a lower Q. A higher Q is achieved by adding a fast region at an end of one or more of the electrode fingers of the IDT.

A filter (10) includes a series arm circuit (11) and a parallel arm circuit (12). The parallel arm circuit (12) includes a parallel arm resonator (p1), a variable frequency circuit (12T), and a parallel arm resonator (p2) connected in parallel with a circuit in which the parallel arm resonator (p1) and the variable frequency circuit (12T) are connected in series. The variable frequency circuit (12T) includes a parallel arm resonator (p3) and a switch (SW) connected in parallel with the parallel arm resonator (p3), and is configured to change frequencies of a pass band and a frequency of an attenuation pole by switching between an on state and off state of the switch (SW). A resonant frequency and anti-resonant frequency of the parallel arm resonator (p1) are respectively different from a resonant frequency and anti-resonant frequency of the parallel arm resonator (p2).