Abstract: An acoustic wave device includes: a substrate; a lower electrode, an air gap being interposed between the lower electrode and the substrate; a piezoelectric film located on the lower electrode; and an upper electrode located on the piezoelectric film such that a resonance region where at least a part of the piezoelectric film is interposed between the upper electrode and the lower electrode is formed and the resonance region overlaps with the air gap in plan view, wherein a surface facing the substrate across the air gap of the lower electrode in a center region of the resonance region is positioned lower than a surface closer to the piezoelectric film of the substrate in an outside of the air gap in plan view.

Abstract: A piezoelectric thin film resonator includes: a substrate; a piezoelectric film located on the substrate; a lower electrode and an upper electrode facing each other across at least a part of the piezoelectric film; and an insertion film that is inserted between the lower electrode and the upper electrode, is located in an outer peripheral region within a resonance region where the lower electrode and the upper electrode face each other across the piezoelectric film, is located in a region that is located outside the resonance region and surrounds the resonance region, is not located in a center region of the resonance region, and includes a first part, which is located in the resonance region and has a first film thickness, and a second part, which is located outside the resonance region and has a second film thickness, the first film thickness being less than the second film thickness.

Abstract: An acoustic wave device includes: a first resonator that includes a first piezoelectric substance, and first lower and upper electrodes sandwiching the first piezoelectric substance in a direction of a c-axis orientation or a polarization axis of the first piezoelectric substance; and a second resonator that is located closer to a signal input terminal than the first resonator is, is connected in series to the first resonator, includes a second piezoelectric substance, and second lower and upper electrodes sandwiching the second piezoelectric substance so that an electrode in a direction of the c-axis orientation or a polarization axis of the second piezoelectric substance has an electric potential identical to an electric potential of an electrode of the first resonator in the direction of the c-axis orientation or the polarization axis of the first piezoelectric substance, and has an antiresonant frequency less than an antiresonant frequency of the first resonator.

Abstract: An acoustic wave device includes: a substrate; a lower electrode, an air gap being interposed between the lower electrode and the substrate; a piezoelectric film located on the lower electrode; and an upper electrode located on the piezoelectric film such that a resonance region where at least a part of the piezoelectric film is interposed between the upper electrode and the lower electrode is formed and the resonance region overlaps with the air gap in plan view, wherein a surface facing the substrate across the air gap of the lower electrode in a center region of the resonance region is positioned lower than a surface closer to the piezoelectric film of the substrate in an outside of the air gap in plan view.

Abstract: An acoustic wave device includes: a substrate; an acoustic reflection layer located in or on the substrate and including an air gap, or an acoustic mirror; a piezoelectric film located on the acoustic reflection layer; lower and upper electrodes located on the acoustic reflection layer so as to sandwich the piezoelectric film so that resonance regions are located within the acoustic reflection layer and share the acoustic reflection layer, one of the lower and upper electrodes being divided, another one of the lower and upper electrodes being not divided, the lower and upper electrodes facing each other across the piezoelectric film in each of the resonance regions; and an insertion film located between the lower and upper electrodes, located in at least a part of an outer peripheral region of each of the resonance regions, and being not located in a center region of each of the resonance regions.

Abstract: A filter includes: one or more series resonators connected in series between an input terminal and an output terminal, the one or more series resonators including a series resonator located closest to the output terminal, the series resonator located closest to the output terminal having a resonant frequency that is 99.6% or less of or 102.2% or greater of a center frequency of a passband; one or more parallel resonators connected in parallel between the input terminal and the output terminal; and an inductor connected in parallel to the series resonator located closest to the output terminal.

Abstract: A filter includes: a first substrate; first and second piezoelectric thin film resonators located on the first substrate, each of the resonators including first and second electrodes facing each other across a piezoelectric film, a crystal orientation from the first electrode to the second electrode of the piezoelectric film being the same between the resonators, the first electrodes of the resonators connecting to each other in a connection region between resonance regions where the first and second electrodes face each other across the piezoelectric film, the second electrodes of the resonators failing to connect to each other, and an area of the resonance region being approximately the same between the resonators, a second substrate mounting the first substrate across an air gap; and a ground pattern located on the second substrate and not overlapping with the first electrode located in the resonance regions and the connection region.

Abstract: An acoustic wave device includes: a piezoelectric thin film resonator that is connected between a first node and a second node; and a resonant circuit that is connected in parallel with the piezoelectric thin film resonator between the first node and the second node, and has a resonant frequency f0 that meets a condition of 2×fa×0.92?f0 where fa represents an antiresonant frequency of the piezoelectric thin film resonator.

Abstract: A duplexer includes: a first filter connected between a common terminal and a first terminal and including first series and first parallel resonators; a second filter having a passband higher than that of the first filter, connected between the common terminal and a second terminal, and including second series and second parallel resonators; a first chip including the first series and second parallel resonators mounted thereon; a second chip including the first parallel and second series resonators mounted thereon, wherein when GA and HGB represent temperature coefficients of antiresonant frequencies of the first and second series resonators, and HGA and GB represent temperature coefficients of resonant frequencies of the first and second parallel resonators, a magnitude relationship among GA, GB, HGA, and HGB is none of a relationship in which GA (GB) differs from HGA (HGB), and GB (GA) and HGB (HGA) are located between GA (GB) and HGA (HGB).

Abstract: An acoustic wave filter includes: series resonators connected in series; and one or more parallel resonators connected in parallel, wherein at least two series resonators and a parallel resonator therebetween are divided into a first divided resonator, which includes a piezoelectric substance sandwiched between a pair of electrodes in a c-axis orientation direction, and a second divided resonator, which includes another piezoelectric substance sandwiched between another pair of electrodes so that the another pair of electrodes in the c-axis orientation direction has an electric potential opposite to that of the electrodes of the first divided resonator in the c-axis orientation direction, a first group including the first divided resonators and a second group including the second divided resonators are interconnected in parallel between two nodes, and the first divided resonators and the second divided resonators of the at least two series resonators are not electrically interconnected at the two nodes.

Abstract: A piezoelectric thin film resonator includes: a substrate; a piezoelectric film located on the substrate; a lower electrode and an upper electrode facing each other across at least a part of the piezoelectric film; and an insertion film that is inserted between the lower electrode and the upper electrode, is located in an outer peripheral region within a resonance region where the lower electrode and the upper electrode face each other across the piezoelectric film, is located in a region that is located outside the resonance region and surrounds the resonance region, is not located in a center region of the resonance region, and includes a first part, which is located in the resonance region and has a first film thickness, and a second part, which is located outside the resonance region and has a second film thickness, the first film thickness being less than the second film thickness.

Abstract: A filter includes: a first substrate; first and second piezoelectric thin film resonators located on the first substrate, each of the resonators including first and second electrodes facing each other across a piezoelectric film, a crystal orientation from the first electrode to the second electrode of the piezoelectric film being the same between the resonators, the first electrodes of the resonators connecting to each other in a connection region between resonance regions where the first and second electrodes face each other across the piezoelectric film, the second electrodes of the resonators failing to connect to each other, and an area of the resonance region being approximately the same between the resonators, a second substrate mounting the first substrate across an air gap; and a ground pattern located on the second substrate and not overlapping with the first electrode located in the resonance regions and the connection region.

Abstract: An acoustic wave device includes: a substrate; an acoustic reflection layer located in or on the substrate and including an air gap, or an acoustic mirror; a piezoelectric film located on the acoustic reflection layer; lower and upper electrodes located on the acoustic reflection layer so as to sandwich the piezoelectric film so that resonance regions are located within the acoustic reflection layer and share the acoustic reflection layer, one of the lower and upper electrodes being divided, another one of the lower and upper electrodes being not divided, the lower and upper electrodes facing each other across the piezoelectric film in each of the resonance regions; and an insertion film located between the lower and upper electrodes, located in at least a part of an outer peripheral region of each of the resonance regions, and being not located in a center region of each of the resonance regions.

Abstract: A filter includes: one or more series resonators connected in series between an input terminal and an output terminal, the one or more series resonators including a series resonator located closest to the output terminal, the series resonator located closest to the output terminal having a resonant frequency that is 99.6% or less of or 102.2% or greater of a center frequency of a passband; one or more parallel resonators connected in parallel between the input terminal and the output terminal; and an inductor connected in parallel to the series resonator located closest to the output terminal.

Abstract: An acoustic wave device includes: a piezoelectric thin film resonator that is connected between a first node and a second node; and a resonant circuit that is connected in parallel with the piezoelectric thin film resonator between the first node and the second node, and has a resonant frequency f0 that meets a condition of 2×fa×0.92?f0 where fa represents an antiresonant frequency of the piezoelectric thin film resonator.

Abstract: A duplexer includes: a first filter connected between a common terminal and a first terminal and including first series and first parallel resonators; a second filter having a passband higher than that of the first filter, connected between the common terminal and a second terminal, and including second series and second parallel resonators; a first chip including the first series and second parallel resonators mounted thereon; a second chip including the first parallel and second series resonators mounted thereon, wherein when GA and HGB represent temperature coefficients of antiresonant frequencies of the first and second series resonators, and HGA and GB represent temperature coefficients of resonant frequencies of the first and second parallel resonators, a magnitude relationship among GA, GB, HGA, and HGB is none of a relationship in which GA (GB) differs from HGA (HGB), and GB (GA) and HGB (HGA) are located between GA (GB) and HGA (HGB).

Abstract: An acoustic wave device includes: a first resonator that includes a first piezoelectric substance, and first lower and upper electrodes sandwiching the first piezoelectric substance in a direction of a c-axis orientation or a polarization axis of the first piezoelectric substance; and a second resonator that is located closer to a signal input terminal than the first resonator is, is connected in series to the first resonator, includes a second piezoelectric substance, and second lower and upper electrodes sandwiching the second piezoelectric substance so that an electrode in a direction of the c-axis orientation or a polarization axis of the second piezoelectric substance has an electric potential identical to an electric potential of an electrode of the first resonator in the direction of the c-axis orientation or the polarization axis of the first piezoelectric substance, and has an antiresonant frequency less than an antiresonant frequency of the first resonator.

Abstract: A Lamb wave device according to an embodiment of the present invention includes a piezoelectric function member and a supporting member. The piezoelectric function member has a piezoelectric substrate, IDT electrodes, and a cutout portion. The IDT electrodes are disposed on the upper surface of the piezoelectric substrate. The cutout portion is formed in the piezoelectric substrate, and includes a step face provided between the upper surface and the lower surface of the piezoelectric substrate. The supporting member has a supporting surface and a cavity. The supporting surface is bonded to the lower surface of the piezoelectric substrate, and is exposed in the cutout portion toward the upper surface of the piezoelectric substrate. The cavity is formed adjacent to the supporting surface, and faces the IDT electrodes through the piezoelectric substrate.

Abstract: An acoustic wave filter includes: series resonators connected in series; and one or more parallel resonators connected in parallel, wherein at least two series resonators and a parallel resonator therebetween are divided into a first divided resonator, which includes a piezoelectric substance sandwiched between a pair of electrodes in a c-axis orientation direction, and a second divided resonator, which includes another piezoelectric substance sandwiched between another pair of electrodes so that the another pair of electrodes in the c-axis orientation direction has an electric potential opposite to that of the electrodes of the first divided resonator in the c-axis orientation direction, a first group including the first divided resonators and a second group including the second divided resonators are interconnected in parallel between two nodes, and the first divided resonators and the second divided resonators of the at least two series resonators are not electrically interconnected at the two nodes.

Abstract: A Lamb wave device according to an embodiment of the present invention includes a piezoelectric function member and a supporting member. The piezoelectric function member has a piezoelectric substrate, IDT electrodes, and a cutout portion. The IDT electrodes are disposed on the upper surface of the piezoelectric substrate. The cutout portion is formed in the piezoelectric substrate, and includes a step face provided between the upper surface and the lower surface of the piezoelectric substrate. The supporting member has a supporting surface and a cavity. The supporting surface is bonded to the lower surface of the piezoelectric substrate, and is exposed in the cutout portion toward the upper surface of the piezoelectric substrate. The cavity is formed adjacent to the supporting surface, and faces the IDT electrodes through the piezoelectric substrate.