An acoustic wave element 1 according to the present disclosure includes a piezoelectric substrate 2 and an IDT electrode 3 on the piezoelectric substrate 2. The IDT electrode 3 includes a multilayer structure of a first layer 35 comprised of Al containing 10% or less of a sub-component and a second layer 37 comprised of a CuAl.sub.2 alloy. The second layer 37 enables the acoustic wave element 1 to have excellent electric power resistance.

A multiplexer includes a first matching circuit having one end connected to a common terminal; a first filter that has one end connected to the other end of the first matching circuit and the other end connected to a first terminal; a second matching circuit having one end connected to the common terminal; a second filter that has one end connected to the other end of the second matching circuit and the other end connected to a second terminal; and a third filter that has one end connected to the common terminal and the other end connected to a third terminal. The first matching circuit includes a first inductor connected on a first signal path in the first matching circuit. The second matching circuit includes a second inductor connected between a second signal path in the second matching circuit and ground.

Bandpass filters and methods of designing bandpass filters are disclosed. A bandpass filter includes a plurality of series acoustic resonators connected in series between an input and an output, and a plurality of\ shunt acoustic resonators, each shunt acoustic resonator connected between a ground and one of the input, the output, and a junction between two of the plurality of series acoustic resonators. A first shunt resonator of the plurality of shunt resonators has a motional resonance frequency higher than and adjacent to an upper edge of a passband of the bandpass filter.

In an elastic wave resonator, a first IDT electrode, a second IDT electrode, a first reflector, and a second reflector are located on a piezoelectric substrate. The first IDT electrode and the second IDT electrode share a shared bus bar. Between a first terminal and a second terminal, the first IDT electrode and the second IDT electrode are connected in parallel. The shared bus bar and the first reflector are connected to the first terminal. A first bus bar and a second bus bar are connected to the second reflector, and are further connected to the second terminal.

A radio-frequency module is provided that includes a structure, a filtering element disposed on the structure, a switching element embedded in the structure, and an impedance element connected to the switching element and the filtering element. In a plan view of the structure, the switching element and the filtering element overlap each other in at least part thereof. The structure has a plurality of vias including a via , a via and a via. The via connects the input-output terminal and the filtering element. The via connects the ground terminal and an impedance adjustment circuit including the switching element and the impedance element. In a plan view, the via is located in a smallest rectangular region encompassing the vias.

A composite acoustic wave filter device includes first and second acoustic wave filters. One end of the first acoustic wave filter with a pass band in a relatively low frequency range and one end of the second acoustic wave filter with a pass band in a relatively high frequency range are connected in common. A first end portion of a first parallel capacitance element and a third end portion of a second parallel capacitance element are connected to a signal line of the second acoustic wave filter. A ground-side end portion of the first parallel capacitance element is connected in common to a ground-side end portion of the first acoustic wave filter. A fourth end portion of the second parallel capacitance element is connected to a ground potential.

An acoustic wave filter includes a first filter circuit on a first path and an additional circuit connected to the first path. The first filter circuit includes a series arm resonator and a longitudinally coupled resonator. The longitudinally coupled resonator includes a first acoustic wave resonator and a first reflector. The additional circuit includes a second acoustic wave resonator on the opposite side of the first acoustic wave resonator with respect to the first reflector. The second acoustic wave resonator includes a first end connected to the first path through a second path and a second end connected to ground. The series arm resonator is connected to a portion of the first path between a connection node at which the second acoustic wave resonator is connected to the first path and the longitudinally coupled resonator.

An SAW device 1 includes a piezoelectric substrate 13, an IDT electrode 5 on a first major surface 3a of the piezoelectric substrate 13, a capacitance element 31 which is located on the first major surface 3a and is connected to the IDT electrode 5, and a cover 9 which is superimposed only on the capacitance element 31 between the IDT electrode 5 and the capacitance element 31.

A multiplexer includes a first filter disposed between an antenna common terminal and a first terminal, and a second filter that is disposed between the antenna common terminal and a second terminal and that has higher passband frequencies than the first filter. The second filter includes IDTs that are longitudinally coupled. Among IDT electrodes in the IDTs, first IDT electrodes are connected to the antenna common terminal side, and second IDT electrodes are connected to the second terminal side. The first and second IDT electrodes have different main pitches of the electrode fingers. At least one of the second IDT electrodes out of all of the electrode fingers has a maximum main pitch.

An acoustic wave device, and an acoustic wave filter and electronics module including the same. The acoustic wave device comprises a first interdigital transducer electrode having a first bus bar and a first plurality of electrode fingers extending from the first bus bar, the first bus bar having a width of 3 μm or less in a direction parallel to the extension of the first plurality of electrode fingers, and a second interdigital transducer electrode having a second bus bar and a second plurality of electrode fingers extending from the second bus bar and interleaved with the first plurality of electrode fingers, the second bus bar having a width of 3 μm or less in a direction parallel to the extension of the second plurality of electrode fingers. The acoustic wave device allows for improvements in power durability when used in an acoustic wave filter, without an increase in size of the acoustic wave filter.