The present disclosure provides a film bulk acoustic resonator and a method for fabricating the film bulk acoustic resonator. The resonator includes a carrier substrate; a support layer bonded on the carrier substrate, where the support layer encloses a first cavity exposing the carrier substrate; a piezoelectric stacked structure covering the first cavity, where the piezoelectric stacked structure includes a first electrode, a piezoelectric layer, and a second electrode which are stacked sequentially from a bottom to a top; and protrusions disposed at a boundary of an effective resonance region, where the protrusions are disposed on an upper surface or a lower surface of the piezoelectric stacked structure; or a part of the protrusions is disposed on the upper surface of the piezoelectric stacked structure, and another part of the protrusions is disposed on the lower surface of the piezoelectric stacked structure.

A radio-frequency module includes a mounting substrate, a first filter, a second filter, a shield layer, and a conductor. The mounting substrate has a first main surface and a second main surface on opposite sides. The shield layer is disposed on an outer surface of a resin layer with which the first filter and the second filter are covered. The radio-frequency module is capable of performing simultaneous transmission by using both the first filter and the second filter. The conductor is disposed on the first main surface of the mounting substrate and is in contact with the transmitting filter and the mounting substrate. The conductor is in contact with the shield layer on a side other than a side closer to the second filter than to the first filter.

Acoustic resonators are disclosed. 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. An interdigital transducer (IDT) is formed on the front surface of the piezoelectric plate. The IDT includes: a first busbar and a second busbar disposed on respective portions of the piezoelectric plate other than the diaphragm; a first set of elongate fingers extending from the first bus bar onto the diaphragm; and a second set of elongate fingers extending from the second bus bar onto the diaphragm, the second set of elongate fingers interleaved with the first set of elongate fingers.

A radio frequency filter includes at least a first sub-filter and a second sub-filter connected in parallel between a first port and a second port. Each of the sub-filters has a piezoelectric plate having front and back surfaces, the back surface attached to a substrate, and portions of the piezoelectric plate forming diaphragms spanning respective cavities in the substrate. A conductor pattern is formed on the front surface of the plate, the conductor pattern includes interdigital transducers (IDTs) of a respective plurality of resonators, with interleaved fingers of each IDT disposed on a respective diaphragm of the plurality of diaphragms. A thickness of the portions of the piezoelectric plate of the first sub-filter is different from a thickness of the portions of the piezoelectric plate of the second sub-filter.

A radio frequency filter includes at least a first sub-filter and a second sub-filter connected in parallel between a first port and a second port. Each of the sub-filters has a piezoelectric plate having front and back surfaces, the back surface attached to a substrate, and portions of the piezoelectric plate forming diaphragms spanning respective cavities in the substrate. A conductor pattern is formed on the front surface of the plate, the conductor pattern includes interdigital transducers (IDTs) of a respective plurality of resonators, with interleaved fingers of each IDT disposed on a respective diaphragm of the plurality of diaphragms. A thickness of the portions of the piezoelectric plate of the first sub-filter is different from a thickness of the portions of the piezoelectric plate of the second sub-filter.

An acoustic resonator includes: a resonating unit including a resonating unit including a piezoelectric layer and first and second electrodes disposed on a lower side and an upper side of the piezoelectric layer, respectively; a substrate disposed on a lower side of the resonating unit; a support unit providing a cavity between the substrate and the resonating unit; and an intermediate metal layer separated from the second electrode and disposed in the resonating unit such that at least a portion thereof is surrounded by the piezoelectric layer and the second electrode.

An acoustic wave device includes a piezoelectric film made of lithium niobate or lithium tantalate, first and second busbar electrodes located on the piezoelectric film and opposite to each other, and first and second electrode fingers and each including one end coupled to the first busbar electrode or the second busbar electrode. The acoustic wave device uses bulk waves in a first thickness-shear mode. A first gap is provided between the first busbar electrode and the second electrode finger. A second gap is provided between the second busbar electrode and the first electrode finger. A length of the first gap and the second gap in a direction in which the first and second electrode fingers extend is about 0.92p or longer, where p is a center-to-center distance between the adjacent first and second electrode fingers.

An acoustic wave device includes a piezoelectric film made of lithium niobate or lithium tantalate, first and second busbar electrodes located on the piezoelectric film and opposite to each other, and first and second electrode fingers and each including one end coupled to the first busbar electrode or the second busbar electrode. The acoustic wave device uses bulk waves in a first thickness-shear mode. A first gap is provided between the first busbar electrode and the second electrode finger. A second gap is provided between the second busbar electrode and the first electrode finger. A length of the first gap and the second gap in a direction in which the first and second electrode fingers extend is about 0.92p or longer, where p is a center-to-center distance between the adjacent first and second electrode fingers.

An acoustic wave device includes an electrode finger on a principal surface of a piezoelectric substrate and extending in a Y-axis direction. In the acoustic wave device, an acoustic wave velocity is distributed in an order of an intermediate velocity, a low velocity, and a high velocity from a center of the electrode finger toward outer side portions in the Y-axis direction. The acoustic wave device further includes a dielectric between the piezoelectric substrate and a tip-end portion of the electrode finger. An end surface of the dielectric in the Y-axis direction includes first and second side surfaces. A tilt angle of the first side surface is smaller than a tilt angle of the second side surface.

An acoustic wave device includes an electrode finger on a principal surface of a piezoelectric substrate and extending in a Y-axis direction. In the acoustic wave device, an acoustic wave velocity is distributed in an order of an intermediate velocity, a low velocity, and a high velocity from a center of the electrode finger toward outer side portions in the Y-axis direction. The acoustic wave device further includes a dielectric between the piezoelectric substrate and a tip-end portion of the electrode finger. An end surface of the dielectric in the Y-axis direction includes first and second side surfaces. A tilt angle of the first side surface is smaller than a tilt angle of the second side surface.