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.

An acoustic wave device includes a piezoelectric substrate and an IDT electrode including electrode fingers, a barrier layer on the piezoelectric substrate, and a first layer on the barrier layer, and including Cu as a main component. The first layer includes a first principal surface on a side closest to the piezoelectric substrate, a second principal surface opposite to the first principal surface, and a side surface connected to the first principal surface and the second principal surface. The barrier layer covers the first principal surface 5a and the side surface of the first layer. A thickness of a portion of the barrier layer covering the first principal surface of the first layer is smaller than a thickness of a portion of the barrier layer covering the side surface of the first layer.

An acoustic wave device includes a support substrate including a cavity portion and a support portion, a piezoelectric film on the support portion and including a first and second main surfaces, a functional electrode on the first main surface, and a heat dissipation film on at least one of the first and second main surfaces and includes a semiconductor or an insulator. The functional electrode includes at least one pair of first and second electrodes. When a thickness of the piezoelectric film is dx and a middle-to-middle distance between the first and second electrodes is p, dx/p is about 0.5 or less. The heat dissipation film overlaps at least a portion of the support portion in plan view. A thermal conductivity of the heat dissipation film is higher than a thermal conductivity of the piezoelectric film, and a thickness of the heat dissipation film is less than the thickness of the piezoelectric film.

A bulk acoustic wave resonator is provided. The bulk acoustic wave resonator includes a board; a resonant portion including a first electrode, a piezoelectric layer, and a second electrode, and disposed on the board, and a temperature compensation layer disposed on the resonant portion, wherein the temperature compensation layer includes a temperature compensation portion formed of a dielectric and a loss compensation portion formed of a material different from a material of the temperature compensation portion, and wherein each of the temperature compensation portion and the loss compensation portion includes a plurality of linear patterns, and the linear patterns of the temperature compensation portion and the linear patterns of the loss compensation portion are alternately disposed.

There are disclosed acoustic resonators and radio frequency filter devices. A back surface of a single-crystal piezoelectric plate is attached to a surface of a substrate except for portions of the piezoelectric plate forming a plurality of diaphragms, each of which spans a respective cavity in the substrate. A conductor pattern is formed on the front surface, the conductor pattern including interdigital transducers (IDTs) of one or more pairs of sub-resonators, each pair consisting of two sub-resonators. The IDT of each sub-resonator includes interleaved fingers disposed on a respective diaphragm. The piezoelectric plate and the IDTs are configured such that respective radio frequency signals applied to each IDT excite respective shear primary acoustic modes in the respective diaphragms. The two sub-resonators of each pair of sub-resonators are positioned symmetrically about a central axis.

A bulk acoustic wave resonator includes: a substrate; a membrane layer forming a cavity together with the substrate; a lower electrode disposed on the membrane layer; a piezoelectric layer disposed on a flat surface of the lower electrode; and an upper electrode covering a portion of the piezoelectric layer and exposing a side of the piezoelectric layer to air, wherein the piezoelectric layer includes a step portion extended from the side of the piezoelectric layer and disposed on the flat surface of the lower electrode.

An acoustic resonator includes a substrate, an insulation layer disposed on the substrate, a resonating portion disposed on the insulation layer and having a first electrode, a piezoelectric layer, and a second electrode, stacked thereon, a cavity disposed between the insulation layer and the resonating portion, a protruded portion having a plurality of protrusions disposed on a lower surface of the cavity, and a hydrophobic layer disposed on an upper surface of the cavity and a surface of the protruded portion.

A bulk-acoustic wave resonator includes a substrate, a first electrode disposed on the substrate, a piezoelectric layer, of which at least a portion is disposed on the first electrode, a second electrode disposed on the piezoelectric layer, and a passivation layer disposed to cover the first electrode and the second electrode. Either one or both of the first electrode and the second electrode includes an aluminum alloy layer. Either one or both of the piezoelectric layer and the passivation layer has aluminum nitride, or aluminum nitride added with a doping material, having a ratio of an out-of-plane lattice constant “c” to an in-plane lattice constant “a” (c/a) of less than 1.58.

A bulk-acoustic resonator module includes: a module substrate; a bulk-acoustic resonator connected to the module substrate by a connection terminal and disposed spaced apart from the module substrate; and a sealing portion sealing the bulk-acoustic resonator. The bulk-acoustic resonator includes a resonating portion disposed opposite to an upper surface of the module substrate. A space is disposed between the resonating portion and the upper surface of the module substrate.

An acoustic wave device is disclosed. The acoustic wave deice can include a membrane structure and a support substrate. The membrane structure includes a piezoelectric layer, an interdigital transducer electrode arranged on the piezoelectric layer, and a thermally conductive layer arranged at least partially in contact with the piezoelectric layer. The support substrate is connected to the membrane structure and configured such that a cavity is provided next to the membrane structure. The acoustic wave device can laterally excite a bulk acoustic wave.