Provided are a band-pass filter circuit and a multiplexer. The band-pass filter circuit includes an electromagnetic LC filter circuit and acoustic resonance units. At least one of the acoustic resonance units each includes at least one first acoustic resonator and at least one second acoustic resonator. The first acoustic resonator is connected in series between the band-pass filter circuit and the electromagnetic LC filter circuit. Each of the at least one second acoustic resonator is connected to a terminal of the at least one first acoustic resonator, where the first terminal of the band-pass filter circuit serves as an input terminal or output terminal of the band-pass filter circuit. One or more of the acoustic resonance units are connected on an input side of the electromagnetic LC filter circuit; and the remaining of the acoustic resonance units are connected on an output side of the electromagnetic LC filter circuit.

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 filter (100) includes a piezoelectric layer (105); a first electrode (108), disposed at a first vertical face of the piezoelectric layer (105) and configured to receive an electric signal; and a second electrode (109), disposed at a second vertical face of the piezoelectric layer (105) and configured to output an electric signal, where the first vertical face and the second vertical face are two opposite sides of the piezoelectric layer (105).

A method of fabricating an RF filter comprising an array of resonators, the method comprising the steps of: (a) Obtaining a removable carrier with release layer; (b) Growing a piezoelectric film on a removable carrier; (c) Applying a first electrode to the piezoelectric film; (d) Obtaining a backing membrane on a cover, with or without prefabricated cavities between the backing film and cover; (e) Attaching the backing membrane to the first electrode; (f) Detaching the removable carrier; (g) Measuring and trimming the piezoelectric film as necessary; (h) Selectively etching away the piezoelectric layer to fabricate discrete resonator islands; (i) Etching down through coatings backing membrane, silicon dioxide and into silicon handle to form trenches; (j) Applying passivation layer into the trenches and around the piezoelectric islands; (k) Depositing a second electrode layer over the dielectric and piezoelectric film islands; (l) Applying connections for subsequent electrical coupling to an interposer; (m) Selectively remove second electrode material leaving coupled resonator arrays; (n) Create gasket around perimeter of the resonator array; (o) Thinning down cover of handle to desired thickness; (p) Optionally fabricating cavities between the silicon membrane and handle; (q) Dicing the wafer into flip chip single unit filter arrays; (r) Obtaining an interposer; (s) Optionally applying a dam to the interposer surface to halt overfill flow; (t) Coupling the flip chip single unit filter array to pads of the interposer by reflow of the solder cap; (u) Encapsulating with polymer overfill; and (v) Singulating into separate filter modules.

A method of fabricating an RF filter comprising an array of resonators comprising the steps of: Obtaining a removable carrier with release layer; Growing a piezoelectric film on a removable carrier; Applying a first electrode to the piezoelectric film; Obtaining a backing membrane on a cover, with or without prefabricated cavities between the backing film and cover; Attaching the backing membrane to the first electrode; Detaching the removable carrier; Measuring and trimming the piezoelectric film as necessary; Selectively etching away the piezoelectric layer to fabricate discrete resonator islands; Etching down through coatings and backing membrane to a silicon dioxide layer between the backing membrane and the cover to form trenches; Applying a passivation layer into the trenches and around the piezoelectric islands; Depositing a second electrode layer over the piezoelectric film islands and surrounding passivation layer; Applying connections for subsequent electrical coupling to an interposer; Selectively removing second electrode material leaving coupled resonator arrays; Creating a gasket around perimeter of the resonator array; Thinning down cover to desired thickness; Optionally fabricating upper cavities between the backing membrane and cover by drilling holes through the cover and then selectively etching away the silicon dioxide; Dicing the wafer into flip chip single unit filter arrays; Obtaining an interposer; Optionally applying a dam to the interposer surface to halt overfill flow; Coupling the flip chip single unit filter array to pads of the interposer by reflow of the solder cap; Encapsulating with polymer underfill/overfill; and Singulating into separate filter modules.

An RF triplexer circuit device using modified lattice, lattice, and ladder circuit topologies. The devices can include four resonator devices and four shunt resonator devices. In the ladder topology, the resonator devices are connected in series from an input port to an output port while shunt resonator devices are coupled the nodes between the resonator devices. In the lattice topology, a top and a bottom serial configurations each includes a pair of resonator devices that are coupled to differential input and output ports. A pair of shunt resonators is cross-coupled between each pair of a top serial configuration resonator and a bottom serial configuration resonator. The modified lattice topology adds baluns or inductor devices between top and bottom nodes of the top and bottom serial configurations of the lattice configuration. These topologies may be applied using single crystal or polycrystalline bulk acoustic wave (BAW) resonators.

An integrated circuit film bulk acoustic resonator (FBAR) device having multiple resonator thicknesses is formed on a common substrate in a stacked configuration. In an embodiment, a seed layer is deposited on a substrate, and one or more multi-layer stacks are deposited on the seed layer, each multi-layer stack having a first metal layer deposited on a first sacrificial layer, and a second metal layer deposited on a second sacrificial layer. The second sacrificial layer can be removed and the resulting space is filled in with a piezoelectric material, and the first sacrificial layer can be removed to release the piezoelectric material from the substrate and suspend the piezoelectric material above the substrate. More than one multi-layer stack can be added, each having a unique resonant frequency. Thus, multiple resonator thicknesses can be achieved on a common substrate, and hence, multiple resonant frequencies on that same substrate.

A filter device includes at least one series arm resonator connected in series in a signal line and including first and second end portions, parallel arm resonators connected between the signal line and ground, and a capacitor. The parallel arm resonators include a first parallel arm resonator connected on a first end portion side of the at least one series arm resonator, and a second parallel arm resonator connected on a second end portion side of the at least one series arm resonator. The first parallel arm resonator includes a third parallel arm resonator and a fourth parallel arm resonator each connected to the first end portion. The third parallel arm resonator is connected directly to the ground and the fourth parallel arm resonator is connected to the ground via the capacitor.

A surface acoustic wave device is disclosed. The surface acoustic wave device can include a ceramic substrate, a piezoelectric layer over the ceramic substrate, and an interdigital transducer electrode over the piezoelectric layer. The ceramic substrate can be a polycrystalline spinel substrate. The surface acoustic wave device can also include a temperature compensating layer over the interdigital transducer electrode.