A BAW device comprises a first BAW resonator (1) and a second BAW resonator (2). The first BAW resonator and the second BAW resonator each comprise a first electrode (11, 21), a second electrode (12, 22) and a piezoelectric layer (13, 23) being arranged in each case between the first electrode and the second electrode of the associated BAW resonator. The first electrodes, the second electrodes and the piezoelectric layers of both BAW resonators are designed essentially identically. A first conductor track (24) extends from the first electrode of the second BAW resonator to a third electric element (3) of the BAW device and electrically connects said first electrode with said third electric element. A first dummy conductor track (14) extends from the first electrode of the first BAW resonator, is electrically connected to said first electrode and, apart from said first electrode, is not electrically connected to any further electric element. The first dummy conductor track is designed such that it influences the acoustic and capacitive properties of the first BAW resonator essentially in the same way as the first conductor track influences the acoustic and capacitive properties of the second BAW resonator.

A piezoelectric element includes a second electrode layer on a second surface of a single-crystal piezoelectric layer. A hole continuous with a through-hole is provided in the second electrode layer. The second electrode layer is made of Pt, Ti, Al, Cu, Au, Ag, Mg, or an alloy including at least one of the metals as a main ingredient. A third electrode layer is on one side of the second electrode layer opposite to the single-crystal piezoelectric layer. The third electrode layer includes at least a portion outside of an edge of the hole with a distance maintained relative to the edge of the hole when viewed in a direction perpendicular or substantially perpendicular to the second surface. The third electrode layer is made of Ni or an alloy including Ni as a main ingredient.

Aspects of this disclosure relate to bulk acoustic wave components. A bulk acoustic wave component can include a substrate, at least one bulk acoustic wave resonator on the substrate, and a cap enclosing the at least one bulk acoustic wave resonator. The cap can include a sidewall spaced apart from an edge of the substrate. The sidewall can be 5 microns or less from the edge of the substrate.

A BAW resonance device comprises a first layer including a cavity located on a first side, a first electrode having a first end located in the cavity and a second end contacting with the first layer, a second layer located on the first side, and a second electrode located on the second layer above the cavity, wherein the first electrode and the second electrode are located on two sides of the second layer. The first electrode comprises a first electrode layer and a second electrode layer, and the second electrode layer and the second layer are located on two sides of the first electrode layer. The second electrode comprises a third electrode layer and a fourth electrode layer, and the second layer and the fourth electrode layer are located on two sides of the third electrode layer. Thus, the electrical resistance is lowered and the electrical losses are reduced.

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.

The present disclosure provides a bulk acoustic wave resonator, a manufacturing method thereof, and a filter, wherein the bulk acoustic wave resonator includes: a substrate; an acoustic reflection unit on the substrate; a piezoelectric stack structure on the acoustic reflection unit; and a pad on the piezoelectric stack structure; wherein the pad has an overlapping region with the acoustic reflection unit. The acoustic wave resonator, the manufacturing method thereof and the filter of the present disclosure can effectively reduce connection resistance of the bulk acoustic wave resonator, thereby reducing insertion loss of the filter.

Acoustic resonator devices and filters are disclosed. An acoustic resonator includes a substrate having a trap-rich region adjacent to a surface and a single-crystal piezoelectric plate having parallel front and back surfaces, the back surface attached to the 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 single-crystal piezoelectric plate such that interleaved fingers of the IDT are disposed on the diaphragm. The single-crystal piezoelectric plate and the IDT are configured such that a radio frequency signal applied to the IDT excites a shear primary acoustic mode within the diaphragm.

A film bulk acoustic resonator (FBAR) structure includes a bottom cap wafer, a piezoelectric layer disposed on the bottom cap wafer, the piezoelectric layer including a single crystalline piezoelectric material, a bottom electrode disposed below the piezoelectric layer; a top electrode disposed above the piezoelectric layer; and a cavity disposed below the bottom electrode.

Devices and processes for preparing devices are described for a bulk acoustic wave resonator. A stack includes a first electrode that is coupled to a first side of a piezoelectric layer and a second electrode that is coupled to a second side of the piezoelectric layer. The stack is configured to resonate in response to an electrical signal applied between the first electrode and the second electrode. A cavity frame is coupled to the first electrode and to the substrate. The cavity frame forms a perimeter around a cavity. Optionally, a heat dissipating frame is formed and coupled to the second electrode. The cavity frame and/or the heat dissipating frame improve the thermal stability of the bulk acoustic resonator.

The present disclosure provides a bulk acoustic wave resonator, a manufacturing method thereof, and a filter, wherein the bulk acoustic wave resonator includes: a substrate; an acoustic reflection unit on the substrate; a piezoelectric stack structure on the acoustic reflection unit; and a pad on the piezoelectric stack structure; wherein the pad has an overlapping region with the acoustic reflection unit. The acoustic wave resonator, the manufacturing method thereof and the filter of the present disclosure can effectively reduce connection resistance of the bulk acoustic wave resonator, thereby reducing insertion loss of the filter.