An elastic wave device manufacturing method includes a preparing a piezoelectric wafer on which IDT electrodes are provided in elastic wave device forming portions, providing on a first main surface of the piezoelectric wafer support layers in the elastic wave device forming portions, bonding a cover member to cover the support layers to obtain a multilayer body, cutting the multilayer body in a first direction multiple times, cutting the multilayer body in a second direction orthogonal to the first direction to obtain elastic wave devices, in which a resin layer extends across a boundary between the elastic wave device forming portions adjacent to each other on the first main surface of the piezoelectric wafer, and the second cutting step is performed in a state in which the resin layer is present.

An acoustic wave device includes a support substrate made of silicon, a piezoelectric body provided directly or indirectly on the support substrate, the piezoelectric body including a pair of main surfaces facing each other, and an interdigital transducer electrode provided directly or indirectly on at least one of the main surfaces of the piezoelectric body, a wave length that is determined by an electrode finger pitch of the interdigital transducer electrode being λ. An acoustic velocity V.sub.Si=(V.sub.1).sup.1/2 of bulk waves that propagate in the support substrate, which is determined by V.sub.1 out of solutions V.sub.1, V.sub.2, V.sub.3 of x derived from the expression, Ax.sup.3+Bx.sup.2+Cx+D=0, is higher than or equal to about 5500 m/s.

An acoustic wave device includes a support substrate made of silicon, a piezoelectric body provided directly or indirectly on the support substrate, the piezoelectric body including a pair of main surfaces facing each other, and an interdigital transducer electrode provided directly or indirectly on at least one of the main surfaces of the piezoelectric body, a wave length that is determined by an electrode finger pitch of the interdigital transducer electrode being λ. An acoustic velocity V.sub.Si=(V.sub.1).sup.1/2 of bulk waves that propagate in the support substrate, which is determined by V.sub.1 out of solutions V.sub.1, V.sub.2, V.sub.3 of x derived from the expression, Ax.sup.3+Bx.sup.2+Cx+D=0, is higher than or equal to about 5500 m/s.

An acoustic wave filter device includes at least one series arm resonator and a parallel arm resonator. The series arm resonators and the parallel arm resonator are defined by acoustic wave resonators, an interdigital transducer electrode of the series arm resonators is an apodized interdigital transducer electrode subjected to apodization weighting, in the interdigital transducer electrode of the parallel arm resonator, an intersecting portion includes a central region and low acoustic velocity regions provided at both outer side portions of the central portion, an acoustic velocity of an acoustic wave in the low acoustic velocity region is lower than an acoustic velocity of an acoustic wave in the central region, and a high acoustic velocity region where an acoustic velocity of an acoustic wave is higher than that of the low acoustic velocity region is provided at an outer side portion of each of the low acoustic velocity regions.

A radio-frequency circuit is capable of simultaneously transmitting a radio-frequency signal of a middle high band group (MHB) including B1 and B3, and a radio-frequency signal of a ultra-high band group (UHB) including n77, and includes: a first transfer circuit that transfers the MHB radio-frequency signal and a radio-frequency signal of a low band group (LB); and a second transfer circuit that transfers the UHB radio-frequency signal. The first transfer circuit includes: a power amplifier for B1 signals; a diplexer that demultiplexes and/or multiplexes the MHB radio-frequency signal and the LB radio-frequency signal; a transmission filter that is connected to the power amplifier and has, as a passband, a transmission band of B1; and a band-elimination filter that is disposed between the diplexer and the transmission filter, and has, as an attenuation band, a transmission band of n77. The second transfer circuit includes a power amplifier for n77 signals.

An exemplary embodiment of the present disclosure provides a multiplexer/demultiplexer, comprising a plurality of unit cells arranged in a lattice, a first domain, a second domain, a third domain, and a controller. Each of the unit cells can comprise a topological-insulative material, a first piezoelectric patch, and a second piezoelectric patch. A first domain can comprise a first portion of the plurality of unit cells. A second domain can comprise a second portion of the plurality of unit cells. A third domain can comprise a third portion of the plurality of unit cells. The controller can be configured to: apply a negative capacitance to the first piezoelectric patches in the first domain; apply a negative capacitance to the second piezoelectric patches in the second domain; and alternately apply a negative capacitance to the first and second piezoelectric patches, respectively, in the third domain.

An exemplary embodiment of the present disclosure provides a multiplexer/demultiplexer, comprising a plurality of unit cells arranged in a lattice, a first domain, a second domain, a third domain, and a controller. Each of the unit cells can comprise a topological-insulative material, a first piezoelectric patch, and a second piezoelectric patch. A first domain can comprise a first portion of the plurality of unit cells. A second domain can comprise a second portion of the plurality of unit cells. A third domain can comprise a third portion of the plurality of unit cells. The controller can be configured to: apply a negative capacitance to the first piezoelectric patches in the first domain; apply a negative capacitance to the second piezoelectric patches in the second domain; and alternately apply a negative capacitance to the first and second piezoelectric patches, respectively, in the third domain.

An acoustic wave resonator includes two comb-shaped electrodes provided on a piezoelectric substrate, each of the comb-shaped electrodes including electrode fingers and a bus bar coupled to the electrode fingers, an acoustic velocity of an acoustic wave propagating through a gap region, which is located between tips of electrode fingers of one of the comb-shaped electrodes and a bus bar of the other of the comb-shaped electrodes, being equal to or greater than 0.98 times and equal to or less than 1.02 times an acoustic velocity of an acoustic wave propagating through an edge region located in an edge in an extension direction of the electrode fingers in an overlap region, and an additional film that is provided over the piezoelectric substrate from the edge region to the gap region and is not provided in a center region located further in than the edge region in the overlap region.

An acoustic wave resonator includes two comb-shaped electrodes provided on a piezoelectric substrate, each of the comb-shaped electrodes including electrode fingers and a bus bar coupled to the electrode fingers, an acoustic velocity of an acoustic wave propagating through a gap region, which is located between tips of electrode fingers of one of the comb-shaped electrodes and a bus bar of the other of the comb-shaped electrodes, being equal to or greater than 0.98 times and equal to or less than 1.02 times an acoustic velocity of an acoustic wave propagating through an edge region located in an edge in an extension direction of the electrode fingers in an overlap region, and an additional film that is provided over the piezoelectric substrate from the edge region to the gap region and is not provided in a center region located further in than the edge region in the overlap region.

A radio-frequency filter includes a series-arm circuit on a circuit path that connects a first input/output terminal and a second input/output terminal. A parallel-arm circuit is connected to a node on the path and ground. The series-arm circuit includes a first impedance element, a first switch element connected to the first impedance element, and a series-arm resonator connected in parallel to the first impedance element and the first switch element. The parallel-arm circuit includes a first parallel-arm resonator, and a first switch circuit connected in series to the first parallel-arm resonator, the first switch circuit includes a second switch element. The first and second switch elements and the second switch elements include one or more transistors, and a gate width of the transistors included in the second switch element is larger than that of at least one of the transistors included in the first switch element.