An acoustic wave resonator includes a substrate; a resonating part disposed on a first surface of the substrate and including a first electrode, a piezoelectric layer, and a second electrode; and a cap disposed on the first surface of the substrate and including an accommodating part accommodating the resonating part. The resonating part is configured to be operated by either one or both of a signal output from a first device substrate disposed facing a second surface of the substrate on an opposite side of the substrate from the first surface of the substrate and a signal output from a second device substrate disposed on the cap.

The deterioration in characteristics of a filter is reduced. In a high frequency module, the filter includes a first substrate, a first functional electrode provided on the first substrate and forming a part of an antenna end resonator, a second substrate separate from the first substrate, and a second functional electrode provided on the second substrate and forming a part of at least one acoustic wave resonator other than the antenna end resonator among a plurality of acoustic wave resonators. A first electronic component including the first substrate and the first functional electrode is disposed on the first main surface of the mounting substrate. An inductor is adjacent to the first electronic component in a plan view from a thickness direction of the mounting substrate. The inductor does not overlap the antenna end resonator in a side view from a direction of a winding axis of a winding portion.

The deterioration in characteristics of a filter is reduced. In a high frequency module, the filter includes a first substrate, a first functional electrode provided on the first substrate and forming a part of an antenna end resonator, a second substrate separate from the first substrate, and a second functional electrode provided on the second substrate and forming a part of at least one acoustic wave resonator other than the antenna end resonator among a plurality of acoustic wave resonators. A first electronic component including the first substrate and the first functional electrode is disposed on the first main surface of the mounting substrate. An inductor is adjacent to the first electronic component in a plan view from a thickness direction of the mounting substrate. The inductor does not overlap the antenna end resonator in a side view from a direction of a winding axis of a winding portion.

An acoustic resonator is fabricated by bonding a first piezoelectric plate to a substrate and spans locations for a first and second cavity in the substrate. A top surface of the first piezoelectric plate is planarized to a first thickness. A bonding layer is formed on the first piezoelectric plate and spans the first and second cavity locations. A second piezoelectric plate is bonded to the bonding layer and spans the first and second cavity locations. A portion of the second piezoelectric plate spanning the second cavity location is etched away to form a first membrane over the first cavity location and a second membrane over the second cavity location. Interdigital transducers are formed on the first and second membranes over the first and second cavity location to form a first and second resonator on the same die.

A piezoelectric thin film comprises aluminum nitride containing a monad and at least one type among a tetrad and a pentad. The piezoelectric thin film having a large electromechanical coupling factor and a small stiffness.

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.

Reconfigurable bulk acoustic wave (BAW) devices include one or more ferroelectric materials as the transduction layer(s). A polarization state of at least one of the ferroelectric material(s) is adjusted by applying a bias voltage across electrodes of the BAW device. The application of the bias voltage can change one or more properties of the ferroelectric material, which in turn may change a response of the BAW device.

A bulk acoustic wave (BAW) resonator is disclosed. The BAW resonator includes: a lower electrode; a piezoelectric layer disposed over the lower electrode; and an upper electrode over the piezoelectric layer. An opening having a first area exists in and extends completely through the upper electrode. The BAW resonator also includes a substrate disposed below the lower electrode; a cavity; and a pillar disposed in the cavity and extending to contact a portion of the lower electrode disposed beneath the opening. The pillar has a second area that is less than the first area. There are no electrical connections that extend across the opening from one side to another.

A germanium-containing aluminum nitride piezoelectric film and a method for manufacturing an aluminum nitride piezoelectric film in which a germanium-containing aluminum nitride piezoelectric film is grown on a substrate by sputtering.

A filter includes: series resonators connected to each other in series; shunt resonators connected to first nodes between some of the series resonators; and a variable capacitor connected to a second node between some of the series resonators, and forming a pole configured to suppress harmonics.