A method of forming a piezoelectric thin film includes sputtering a first surface of a substrate to provide a piezoelectric thin film comprising AlN, AlScN, AlCrN, HfMgAlN, or ZrMgAlN thereon, processing a second surface of the substrate that is opposite the first surface of the substrate to provide an exposed surface of the piezoelectric thin film from beneath the second surface of the substrate, wherein the exposed surface of the piezoelectric thin film includes a first crystalline quality portion, removing a portion of the exposed surface of the piezoelectric thin film to access a second crystalline quality portion that is covered by the first crystalline quality portion, wherein the second crystalline quality portion has a higher quality than the first crystalline quality portion and processing the second crystalline quality portion to provide an acoustic resonator device on the second crystalline quality portion.

A film bulk acoustic wave resonator (BAWR) includes a first substrate; a first insulating material layer; and a first cavity, formed in the first insulating material layer. The film BAWR also includes a first electrode containing a first electrode cavity; a second electrode containing a second electrode cavity; and a first piezoelectric oscillation plate, sandwiched between the first electrode and the second electrode. Without having any parallel edges, the boundary of the first piezoelectric oscillation plate is entirely enclosed in the first cavity boundary, and at least includes an overlapping region of the boundary of the first electrode cavity and the boundary of the second electrode cavity. The film BAWR further includes a plurality of second and third piezoelectric oscillation plates, disposed between the first electrode and the second electrode to receive and absorb vibration energy transmitted out through vibration waves induced in the first electrode and the second electrode.

An acoustic resonator package includes a substrate, an acoustic resonator disposed on the substrate, the acoustic resonator including a first hydrophobic layer, a cap configured to accommodate the acoustic resonator, a bonding portion configured to bond the substrate to the cap, and a second hydrophobic layer disposed on the substrate at a position between the acoustic resonator and the bonding portion.

In an array of single crystal acoustic resonators, the effective coupling coefficient of first and second strained single crystal filters are individually tailored in order to achieve desired frequency responses. In a duplexer embodiment, the effective coupling coefficient of a transmit band-pass filter is lower than the effective coupling coefficient of a receive band-pass filter of the same duplexer. The coefficients can be tailored by varying the ratio of the thickness of a piezoelectric layer to the total thickness of electrode layers or by forming a capacitor in parallel with an acoustic resonator within the filter for which the effective coupling coefficient is to be degraded. Further, a strained piezoelectric layer can be formed overlying a nucleation layer characterized by nucleation growth parameters, which can be configured to modulate a strain condition in the strained piezoelectric layer to adjust piezoelectric properties for improved performance in specific applications.

A BAW resonator/filter with a monolithic TFE package that defines an acoustic BC and suppresses resonances from the low-Q piezoelectric area of the resonator and resulting devices are provided. Embodiments include a BAW resonator over a dielectric layer, the BAW resonator including a first metal layer, a thin-film piezoelectric layer, and a second metal layer; a first cavity in the dielectric layer under the first metal layer and a second cavity over the first cavity on the second metal layer; and a pair of TFE anchors on the second metal layer, each TFE anchor adjacent to and on an opposite side of the second cavity and extending beyond the first metal layer.

A fine dust concentration sensor includes a bulk acoustic resonator and a cap including an upper portion with holes therein and a lateral portion connected to the upper portion to accommodate the bulk acoustic resonator. An upper surface of the upper portion of the cap is coated with a hydrophobic material.

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.

A method of fabricating an acoustic wave device includes: forming a piezoelectric thin film resonator and a second lower electrode on a substrate, the piezoelectric thin film resonator having a resonance region in which a first lower electrode and a first upper electrode face each other across a piezoelectric film, the piezoelectric film and the first upper electrode are not formed on the second lower electrode outside the resonance region; forming a first dielectric film in the resonance region and a second dielectric film on the second lower electrode outside the resonance region at a same time, the first dielectric film and the second dielectric film being made of a material different from a material of the piezoelectric film; and forming a second upper electrode on the second dielectric film, the second upper electrode facing the second lower electrode.

A bulk acoustic wave resonator includes a substrate; a lower electrode disposed on the substrate; a piezoelectric layer disposed to cover at least a portion of the lower electrode; an upper electrode disposed to cover at least a portion of the piezoelectric layer; and a passivation layer disposed to cover at least a portion of the upper electrode, wherein the passivation layer includes a non-trimming-processed portion disposed outside an active region of the bulk acoustic wave resonator in which portions of the lower electrode, the piezoelectric layer, and the upper electrode overlap, and having a thickness that is thicker than a thickness of a portion of the passivation layer disposed in the active region.

A method of manufacturing a bulk acoustic wave resonator includes: forming a sacrificial layer on a substrate protection layer; forming a membrane layer on the substrate protection layer to cover the sacrificial layer; and forming a cavity by removing the sacrificial layer using a gas mixture comprising a halide-based gas and an oxygen-containing gas, wherein a mixture ratio of the halide-based gas to the oxygen-containing gas in the gas mixture is in a range from 1.5 to 2.4.