A filter includes a piezoelectric film, an acoustic wave resonator including a functional electrode on the piezoelectric film, a capacitor connected in parallel to the acoustic wave resonator, and a resonator electrically connected to the acoustic wave resonator. The functional electrode includes first and second busbars facing each other and first and second electrodes respectively connected to the first and second busbars. The filter further includes a connection electrode on the piezoelectric film and electrically connecting the capacitor and the second busbar to each other. The capacitor includes the first busbar, an insulation film on the first busbar, and a capacitance electrode on the insulation film and that is electrically insulated from the first busbar.

The invention provides a filter device, an RF front-end device and a wireless communication device. The filter device comprises a substrate, at least one resonance device, a passive device and a connector, wherein the at least one resonance device has a first side and a second side opposite to the first side, the substrate is located on the first side, and the passive device is located on the second side. The at least one resonance device is connected to the passive device through the connector. The RF filter device formed by integrating the resonance device (such as an SAW resonance device or a BAW resonance device) and the passive device (such as an IPD) in one die can broaden the passband width, has a high out-of-band rejection, and occupies less space in an RF front-end chip.

A bulk acoustic resonator includes a substrate, a frequency control layer changing a resonant frequency or antiresonant frequency of the bulk acoustic resonator according to a thickness of the frequency control layer, a piezoelectric layer disposed between the frequency control layer and the substrate, a first electrode disposed between the piezoelectric layer and the substrate, a second electrode disposed between the piezoelectric layer and the frequency control layer, a metal layer connected to the first electrode or the second electrode, and a protective layer disposed between the second electrode and the frequency control layer, wherein the frequency control layer covers a larger area than that of the protective layer.

Acoustic resonator devices, filters, and methods are disclosed. An acoustic resonator includes a substrate, a lithium niobate plate having front and back surfaces, wherein Euler angles of the lithium niobate plate are [0°, β, 0°], where β is greater than or equal to 0° and less than or equal to 60°, and an acoustic Bragg reflector between the surface of the substrate and the back surface of the lithium niobate plate. An interdigital transducer (IDT) is formed on the front surface of the piezoelectric plate. At least one finger of the IDT is disposed in a groove in the lithium niobate plate.

An RF 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.

Acoustic resonators and filter devices, and methods for making acoustic resonators and filter devices. An acoustic resonator includes a substrate having a surface and a single-crystal piezoelectric plate having front and back surfaces. The back surface is attached to the surface of the substrate except for a portion of the piezoelectric plate forming a diaphragm spanning a cavity in the substrate. A conductor pattern formed is formed on the front surface of the piezoelectric plate, including an interdigital transducer (IDT) with interleaved fingers of the IDT on the diaphragm. An insulating layer is formed between the piezoelectric plate and portions of the conductor pattern other than the interleaved fingers.

An elastic wave device in which a recess is provided on an upper side of a support, a piezoelectric thin film covers the recess, and an IDT electrode is provided on an upper surface of the piezoelectric thin film. A plate wave of an S0 mode or SH0 mode is used. A plurality of grooves are provided in the upper surface or lower surface of the piezoelectric thin film at a portion of the piezoelectric thin film that is positioned on a hollow section.

Acoustic resonator devices and filters. An acoustic resonator includes a substrate having a surface and a lithium niobate plate. A back surface of the lithium niobate plate is attached the substrate except for a portion of the lithium niobate plate forming a diaphragm that spans a cavity in the substrate. An interdigital transducer (IDT) is formed on a front surface of the lithium niobate plate such that interleaved fingers of the IDT are disposed on the diaphragm. The IDT and the lithium niobate plate configured such that a radio frequency signal applied to the IDT excites a shear primary acoustic mode within the diaphragm. Euler angles of the lithium niobate plate are [0°, β, 0°], where β is greater than or equal to 40° and less than or equal to 70°.

A film bulk acoustic wave resonator (FBAR) includes a piezoelectric film disposed in a central region defining a main active domain in which a main acoustic wave is generated during operation, and in recessed frame regions disposed laterally on opposite sides of the central region. The piezoelectric film disposed in the recessed frame regions includes a greater concentration of defects than a concentration of defects in the piezoelectric film disposed in the central region.

A laterally coupled multi-mode monolithic filter includes: a substrate; a piezoelectric film formed on the substrate; a ground electrode formed on a first surface of the piezoelectric film; and signal electrodes formed on a second surface of the piezoelectric film and arranged in parallel to each other, the second surface being opposite to the first surface, each of the signal electrodes including a first electrode finger and a second electrode finger, wherein the first electrode finger and the second electrode finger have different electric potentials; adjacent signal electrodes of the signal electrodes are at a distance from each other, the distance being greater than a pitch of the first electrode finger and the second electrode finger.