Abstract: A ladder filter includes series arm resonators, parallel arm resonators, and first and second inductors. Second ends of the parallel arm resonators are connected in common to each other and are connected to a ground potential. A first end of each of the first and second inductors is connected to a series arm, and second ends thereof are connected in common to each other and are connected to the ground potential with a capacitor therebetween.

Abstract: An acoustic wave device includes a piezoelectric layer, at least one pair of electrodes, and a protective film. The piezoelectric layer includes first and second major surfaces opposing each other in a first direction. The at least one pair of electrodes are on at least one of the first and second major surfaces. The protective film covers at least a portion of the pair of electrodes. The protective film includes a first-component insulative film including a first component and in contact with the pair of electrodes, and a second-component insulative film including a second component and located at the surface layer of the protective film. The first-component insulative film has a higher moisture resistance than the second-component insulative film. The second-component insulative film has a higher plasma resistance than the first-component insulative film.

Abstract: An acoustic wave device includes a support including a support substrate, a piezoelectric layer on the support in a first direction, a functional electrode on the piezoelectric layer, and a reinforcement film on the piezoelectric layer. The support includes a space portion that opens on a side of the piezoelectric layer, and an extended passage extending farther toward an outer side than an edge of the space portion in a second direction intersecting the first direction. A through-hole is provided at a position not overlapping the functional electrode in plan view in the first direction, communicates with the extended passage, and penetrates the piezoelectric layer. The reinforcement film is provided in a region between the through-hole and the space portion and overlaps at least a portion of a region where the piezoelectric layer and the extended passage overlap each other in the plan view.

Abstract: An acoustic wave device includes an element substrate, a piezoelectric layer, a functional electrode on the piezoelectric layer, and a mounting substrate. The element substrate includes a gap portion at a position overlapping at least a portion of the functional electrode as seen in a lamination direction of the element substrate and the piezoelectric layer, and the mounting substrate includes a ground electrode at a position overlapping the functional electrode in the lamination direction.

Abstract: An acoustic wave device according to the present invention includes a piezoelectric substrate including a piezoelectric layer, a functional electrode provided on the piezoelectric layer, a first support layer provided on the piezoelectric substrate so as to surround the functional electrode, a covering portion provided on or above the first support layer and including a first main surface positioned on the functional electrode side and a second main surface opposite to the first main surface, a silicon oxide layer provided on the first main surface side of the covering portion, and an inductor provided on the silicon oxide layer and made of a wire. The covering portion is made of silicon. The acoustic wave device further includes one of an amorphous silicon layer and a polysilicon layer provided between the covering portion and the silicon oxide layer.

Abstract: In a composite filter device, a first acoustic wave resonator includes a functional electrode on a first main surface of a first piezoelectric substrate, and a wiring electrode is on the first main surface and is not connected to a signal potential. A support is on the first main surface and surrounds the first acoustic wave resonator. A second piezoelectric substrate is on the support and includes a third main surface closer to the support than a fourth main surface. A second acoustic wave resonator includes a functional electrode on the third main surface. The second acoustic wave resonator is a parallel-arm resonator higher in resonant frequency than any other parallel-arm resonator or a series-arm resonator lower in resonant frequency than any other series-arm resonator. The second acoustic wave resonator and the wiring electrode overlap each other when viewed in plan.

Abstract: An acoustic wave device includes a support substrate, a piezoelectric layer on the support substrate, and a functional element on the piezoelectric layer. The support substrate and the piezoelectric layer each have a rectangular or substantially rectangular shape in plan view from a direction normal to the support substrate. At least one corner portion of the piezoelectric layer has a curved shape or a polygonal shape.

Abstract: A ladder filter includes series arm resonators, parallel arm resonators, and first and second inductors. Second ends of the parallel arm resonators are connected in common to each other and are connected to a ground potential. A first end of each of the first and second inductors is connected to a series arm, and second ends thereof are connected in common to each other and are connected to the ground potential with a capacitor therebetween.

Abstract: An acoustic wave device includes first and second acoustic wave resonator units. In a first IDT electrode of the first acoustic wave resonator unit, an intersecting width region includes a central region and first and second low acoustic velocity regions at outer side portions of the central region. The first and second high acoustic velocity regions include openings along an acoustic wave propagation direction. In the second acoustic wave resonator unit, a second IDT electrode includes a central region and first and second low acoustic velocity regions at outer side portions in an intersecting width direction of the central region. At an outer side portion of the first low acoustic velocity region, openings are at a third busbar. At an outer side portion of the second low acoustic velocity region, openings are not provided for a fourth busbar.

Abstract: An acoustic wave element includes a piezoelectric film, an interdigital transducer electrode on a first principal surface of the piezoelectric film, and a high acoustic velocity member near a second principal surface of the piezoelectric film. A surface of the high acoustic velocity member opposite to the piezoelectric film and a side surface of each of the high acoustic velocity member and the piezoelectric film are covered with resin. At least a portion of the side surface of the high acoustic velocity member is in contact with the resin. A gap is provided between the resin and at least a portion of the side surface of the piezoelectric film.

Abstract: 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.

Abstract: In a multiplexer, input or output terminals of four acoustic wave filters are connected to, among a plurality of terminals provided on piezoelectric substrates, antenna terminals connected to an antenna connection terminal; the four acoustic wave filters include a first acoustic wave filter and a second acoustic wave filter that is located at a farther position from the antenna connection terminal than a position of the first acoustic wave filter in a plan view of a substrate; and among the plurality of terminals, the terminals located at the closest position to the antenna connection terminal in the plan view of the substrate are connected to the second acoustic wave filter as the antenna terminals.

Abstract: In a multiplexer, input or output terminals of four acoustic wave filters are connected to, among a plurality of terminals provided on piezoelectric substrates, antenna terminals connected to an antenna connection terminal; the four acoustic wave filters include a first acoustic wave filter and a second acoustic wave filter that is located at a farther position from the antenna connection terminal than a position of the first acoustic wave filter in a plan view of a substrate; and among the plurality of terminals, the terminals located at the closest position to the antenna connection terminal in the plan view of the substrate are connected to the second acoustic wave filter as the antenna terminals.

Abstract: A multiplexer includes a common terminal, a reception terminal, and transmission terminals; a reception filter between the common terminal and the reception terminal; a transmission filter between the common terminal and the transmission terminal; a transmission filter between the common terminal and the transmission terminal; a first inductor connected in series between the common terminal and the reception filter; a second inductor connected between the transmission terminal and the transmission filter; and a third inductor connected between the transmission terminal and the transmission filter. The first inductor and the second inductor couple with each other through a magnetic field, and the first inductor and the third inductor couple with each other through a magnetic field.

Abstract: In a splitter, a first band pass filter is connected between an antenna terminal and a first terminal, a high pass filter and a second band pass filter are connected between the antenna terminal and a second terminal, a pass band of the second band pass filter is higher than a pass band of the first band pass filter, a cut off frequency of the high pass filter is located closer to the high-frequency side than the pass band of the first band pass filter, the pass band of the second band pass filter is located closer to the high-frequency side than the cut off frequency, and the high pass filter also functions as a notch filter having an anti-resonant frequency in a transition region such that the steepness of the transition region between the pass band of the second band pass filter and the attenuated band is high.

Abstract: A multiplexer includes a common terminal, a reception terminal, and transmission terminals; a reception filter between the common terminal and the reception terminal; a transmission filter between the common terminal and the transmission terminal; a transmission filter between the common terminal and the transmission terminal; a first inductor connected in series between the common terminal and the reception filter; a second inductor connected between the transmission terminal and the transmission filter; and a third inductor connected between the transmission terminal and the transmission filter. The first inductor and the second inductor couple with each other through a magnetic field, and the first inductor and the third inductor couple with each other through a magnetic field.

Abstract: An elastic wave filter device has a center frequency of a reception frequency band. A plurality of parallel arms are connected to a portion of a series arm on a second signal terminal side of a portion in which a first series-arm resonator is provided. Series-arm resonators among the plurality of series-arm resonators other than the first series-arm resonator include a series-arm resonator having a resonant frequency higher than the resonant frequency of the first series-arm resonator. The resonant frequency of the first series-arm resonator is equal to the reception frequency band.

Abstract: In a splitter, a first band pass filter is connected between an antenna terminal and a first terminal, a high pass filter and a second band pass filter are connected between the antenna terminal and a second terminal, a pass band of the second band pass filter is higher than a pass band of the first band pass filter, a cut off frequency of the high pass filter is located closer to the high-frequency side than the pass band of the first band pass filter, the pass band of the second band pass filter is located closer to the high-frequency side than the cut off frequency, and the high pass filter also functions as a notch filter having an anti-resonant frequency in a transition region such that the steepness of the transition region between the pass band of the second band pass filter and the attenuated band is high.

Abstract: An elastic wave filter device has a center frequency of a reception frequency band. A plurality of parallel arms are connected to a portion of a series arm on a second signal terminal side of a portion in which a first series-arm resonator is provided. Series-arm resonators among the plurality of series-arm resonators other than the first series-arm resonator include a series-arm resonator having a resonant frequency higher than the resonant frequency of the first series-arm resonator. The resonant frequency of the first series-arm resonator is equal to the reception frequency band.