Abstract: Provided is an aluminum nitride film in which, aluminum nitride crystal grains containing a metal element differing from aluminum and substituting for aluminum are main crystal grains of a polycrystalline film formed of crystal grains, and a concentration of the metal element in a grain boundary between the aluminum nitride crystal grains in at least one region of first and second regions corresponding to both end portions of the polycrystalline film in a film thickness direction of the polycrystalline film is higher than a concentration of the metal element in a center region of the aluminum nitride crystal grain in the at least one region, and is higher than a concentration of the metal element in a grain boundary between the aluminum nitride crystal grains in a third region located between the first region and the second region in the film thickness direction of the polycrystalline film.

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: A piezoelectric thin film resonator includes: a piezoelectric film located on a substrate; lower and upper electrodes facing each other across a part of the piezoelectric film; and an insertion film located between the lower and upper electrodes, located in a part of an outer peripheral region within a resonance region where the lower and upper electrodes face each other across the piezoelectric film, and not located in a center region of the resonance region, a first width in the resonance region of the insertion film in a first region, where the upper electrode is extracted from the resonance region, being greater than a third width in the resonance region in a third region other than a second region, where the lower electrode is extracted from the resonance region, and the first region, a second width in the resonance region in a second region being the third width or greater.

Abstract: An aluminum nitride film contains a Group IV element and a Group II or Group XII element, and an atomic composition ratio of the Group II or Group XII element to the Group IV element is less than 1.

Abstract: A piezoelectric thin film resonator includes: a substrate; a piezoelectric film located on the substrate; lower and upper electrodes facing each other across the piezoelectric film; a mass load film that is located at least one of a first side, which is closer to the upper electrode, of the piezoelectric film and a second side, which is closer to the lower electrode, of the piezoelectric film, separated from the upper and lower electrodes, and surrounds in plan view a resonance region at least in part, the lower and upper electrodes facing each other across the piezoelectric film in the resonance region; and an acoustic reflection layer that includes the resonance region and the mass load film in plan view, is located in or on the substrate, and includes an air gap or an acoustic mirror in which at least two layers with different acoustic characteristics are stacked.

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 piezoelectric thin film resonator includes: a substrate; lower and upper electrodes located on the substrate; a piezoelectric film that has a lower piezoelectric film mainly composed of aluminum nitride and an upper piezoelectric film mainly composed of aluminum nitride, the lower piezoelectric film and the upper piezoelectric film being in contact with each other in at least a part of a resonance region where the lower electrode and the upper electrode face each other across at least a part of the piezoelectric film, and a fluorine concentration at a boundary face with which the lower piezoelectric film and the upper piezoelectric film are in contact being 0.03 atomic % or less; and an insulating film that is located between the lower piezoelectric film and the upper piezoelectric film in a region other than the at least a part of the resonance region and contains silicon oxide.

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: Provided is an aluminum nitride film in which, aluminum nitride crystal grains containing a metal element differing from aluminum and substituting for aluminum are main crystal grains of a polycrystalline film formed of crystal grains, and a concentration of the metal element in a grain boundary between the aluminum nitride crystal grains in at least one region of first and second regions corresponding to both end portions of the polycrystalline film in a film thickness direction of the polycrystalline film is higher than a concentration of the metal element in a center region of the aluminum nitride crystal grain in the at least one region, and is higher than a concentration of the metal element in a grain boundary between the aluminum nitride crystal grains in a third region located between the first region and the second region in the film thickness direction of the polycrystalline film.

Abstract: A piezoelectric thin film resonator includes: an acoustic reflection layer including an air gap or an acoustic mirror; lower and upper electrodes facing each other in a stacking direction, at least a part of each of the lower and upper electrodes being located on or above the acoustic reflection layer; a piezoelectric film sandwiched between the lower and upper electrodes and including lower and upper piezoelectric films, at least a part of an end face of the piezoelectric film in a film thickness direction being located between outer outlines of the resonance region and the acoustic reflection layer in at least a part of a region surrounding a resonance region; and an insertion film inserted between the lower and upper piezoelectric films, located in at least a part of an outer peripheral region within the resonance region, and not located in a center region of the resonance region.

Abstract: An acoustic wave filter includes series resonators and parallel resonators that have a piezoelectric film on an identical substrate and have a lower electrode and an upper electrode, wherein: one of the series resonators and the parallel resonators have a temperature compensation film on a face of the lower electrode or the upper electrode that is opposite to the piezoelectric film in a resonance region, the compensation film having an elastic constant of a temperature coefficient of which sign is opposite to a sign of a temperature coefficient of an elastic constant of the piezoelectric film; and the other have an added film on the same side as the temperature compensation film on the lower electrode side or the upper electrode side compared to the piezoelectric film in the resonance region in the one of the series resonators and the parallel resonators.

Abstract: A piezoelectric thin film resonator includes: a substrate; a piezoelectric film located on the substrate; lower and upper electrodes facing each other across at least a part of the piezoelectric film; a first insertion layer located between the lower and upper electrodes and located in at least a part of an outer peripheral region within a resonance region in which the lower and upper electrodes face each other across the piezoelectric film, the first insertion layer being not located in a center region of the resonance region; and a second insertion layer located between the lower and upper electrodes and located in at least a part of the outer peripheral region, the second insertion layer being not located in the center region, a position of an edge of the second insertion layer being different from a position of an edge of the first insertion film in the resonance region.

Abstract: A piezoelectric thin film resonator includes: lower and upper electrodes located on a substrate and facing each other; a piezoelectric film sandwiched between the lower and upper electrodes and including lower and upper piezoelectric films, an outer outline of the upper piezoelectric film coinciding with or being located further out than an outer outline of a resonance region in a region surrounding the resonance region, the outer outline of the upper piezoelectric film being located further in than an outer outline of the lower piezoelectric film in the region; an insertion film interposed between the lower and upper piezoelectric films, located in an outer peripheral region within the resonance region, not located in a central region of the resonance region, and located on an upper surface of the lower piezoelectric film in the region; and a protective film located on the upper electrode in the resonance region, and located so as to cover an end face of the upper piezoelectric film and an upper surface of t

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 piezoelectric thin film resonator includes: a substrate; a lower electrode and an upper electrode located on the substrate; a piezoelectric film, at least a part of the piezoelectric film being sandwiched between the upper electrode and the lower electrode, the piezoelectric film including a discontinuous portion in which the piezoelectric film discontinues in at least a part of a region surrounding a center region that includes a center of a resonance region where the upper electrode and the lower electrode face each other across the at least a part of the piezoelectric film.

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: A piezoelectric thin film resonator includes: a substrate; a piezoelectric film located on the substrate, the piezoelectric film including an aluminum nitride film containing a II-group or XII-group element and a IV-group or V-group element, a concentration of the IV-group or V-group element being higher than a concentration of the II-group or XII-group element in a middle region in a thickness direction, the concentration of the II-group or XII-group element being higher than the concentration of the IV-group or V-group element in at least one of end regions in the thickness direction; and a lower electrode and an upper electrode facing each other across the piezoelectric film.

Abstract: An acoustic wave device includes: a piezoelectric film made of an aluminum nitride film containing a divalent element and a tetravalent element, or a divalent element and a pentavalent element; and an electrode that excites an acoustic wave propagating through the piezoelectric film.