A cavity structure of a bulk acoustic resonator and a manufacturing process. The cavity structure comprises a substrate and a cavity formed on the substrate, a support layer is arranged on the substrate to form the cavity in a surrounding manner, a release channel in communication with the cavity is formed above the substrate in a same layer with the cavity, and the release channel extends, in parallel to the substrate, in a peripheral area of the cavity. There is no need to manufacture a release hole, which simplifies the manufacturing process of the resonator, thereby avoiding weakening the performance of the resonator due to damage to the structure of the piezoelectric layer around the electrode layer when manufacturing the release hole.

A transducer includes first and second piezoelectric layers made of corresponding different first and second piezoelectric materials and three or more electrodes, implemented in two or more conductive electrode layers. The first piezoelectric layer is sandwiched between a first pair of electrodes and the second piezoelectric layer is sandwiched between a second pair of electrodes. The first and second pairs of electrodes contain no more than one electrode that is common to both pairs.

An acoustic resonator includes a substrate and a resonant portion. The resonant portion has a central portion in which a first electrode, a first piezoelectric layer, a second piezoelectric layer, and a second electrode are stacked in order on the substrate, and an extension portion extending outwardly from the central portion and including an insertion layer. A ratio of an average thickness of the first piezoelectric layer to an average thickness of the second piezoelectric layer is 18.4% to 40%.

Filter devices and fabrication methods are disclosed. A filter device includes a piezoelectric plate and a conductor pattern on a front surface of the piezoelectric plate. The conductor pattern includes interdigital transducers (IDTs) of a plurality of transversely-excited film bulk acoustic resonators (XBARs) and a plurality of conductors connecting the plurality of XBARs in a ladder filter circuit architecture. The plurality of conductors includes a first conductor adjacent to a second conductor. An opening is provided through the piezoelectric plate between the first conductor and the second conductor.

An acoustic resonator includes: a substrate; a resonant region including a first electrode, a piezoelectric layer, and a second electrode disposed on the substrate, and a reflective layer disposed along a periphery of the resonant region; and a connection electrode extending from the second electrode. The reflective layer includes a second section disposed between the resonant region and the connection electrode, and a first section, and a cross-sectional area of the first section is different than a cross-sectional area of the second section.

An acoustic wave device includes a piezoelectric layer that is made of lithium niobate or lithium tantalate, and a plurality of pairs of electrodes opposed to each other in a direction intersecting with a thickness direction of the piezoelectric layer, in which a bulk wave in a thickness shear primary mode is used or d/p is about 0.5 or lower when a thickness of the piezoelectric layer is d and a distance between centers of mutually adjacent electrodes among the plurality of pairs of electrodes is p. The plurality of pairs of electrodes include at least one pair of first electrodes of a first acoustic wave resonator and at least one pair of second electrodes of a second acoustic wave resonator. A direction orthogonal to a longitudinal direction of the second electrodes in the second acoustic wave resonator is inclined at an angle that is greater than 0° and smaller than 360° with respect to a direction orthogonal to a longitudinal direction of the first electrodes in the first acoustic wave resonator.

An acoustic filter device includes first and second series resonators and at least one shunt resonator, each shunt resonator electrically coupled to the first series resonator or the second series resonator. Each of the first and second series resonators includes respective first and second sub-resonators electrically connected in series, The first sub-resonators of the first and second series resonators are acoustically coupled along a first shared acoustic track. The second sub-resonators of the first and second series resonators are acoustically coupled along a second shared acoustic track.

Acoustic resonator devices, filters, and methods are disclosed. An acoustic resonator includes a substrate and a piezoelectric plate having front and back surfaces, the back surface attached to a surface of the substrate except for a portion of the piezoelectric plate forming a diaphragm that spans a cavity in the substrate. An interdigital transducer (IDT) is formed on the front surface of the piezoelectric plate such that interleaved fingers of the IDT are disposed on the diaphragm. The IDT is configured to excite a primary acoustic mode in the diaphragm in response to a radio frequency signal applied to the IDT. At least one finger of the IDT is disposed in a groove in the diaphragm. A depth of the groove is less than a thickness of the at least one finger of the IDT.

An acoustic wave device includes a support substrate, an inorganic film over the support substrate, a piezoelectric layer over the inorganic film, and an electrode over the piezoelectric layer. A portion of the support substrate includes a hollow that overlaps at least a portion of the electrode in a thickness direction of the support substrate. An inner wall of the inorganic film is located farther from the hollow than a location on an inner wall of the support substrate, the location being closest to the piezoelectric layer, the inner wall of the support substrate defining the hollow.

A bulk acoustic wave (BAW) resonator includes a substrate, a piezoelectric layer disposed above the substrate, a first electrode disposed below the piezoelectric layer, a second electrode disposed above the piezoelectric layer, a first dielectric layer, a second dielectric layer, and a third dielectric layer disposed between the substrate and the piezoelectric layer, and a bonding layer disposed between the third dielectric layer and the substrate. The first dielectric layer is disposed below the piezoelectric layer and includes a cavity. The third dielectric layer is disposed below the first dielectric layer and includes a protruding structure protruding towards the piezoelectric layer. The second dielectric layer overlays the third dielectric layer including the protruding structure, the second dielectric layer and the protruding structure of the third dielectric layer constituting a double-wall boundary structure surrounding the cavity.