Aspects of this disclosure relate to bulk acoustic wave devices that have a piezoelectric layer between a first electrode and a second electrode and a suspended frame structure that is suspended over a gap. The gap can be between the first electrode and the piezoelectric layer or between the second electrode and the piezoelectric layer. The bulk acoustic wave devices can have an inner raised frame portion inside of the suspended frame. The gap can be disposed between portions of the first and second electrodes that extend past an end of the piezoelectric layer. A conductive material can extend through an opening in a passivation layer at a location directly above the gap.

A bulk acoustic wave resonator having a central region, an outer region, and a raised frame region between the central region and the outer region is disclosed. The bulk acoustic wave resonator can include a piezoelectric layer and a top electrode over the piezoelectric layer. The top electrode is disposed at least in the central region, the outer region, and the raised frame region, the top electrode including a first layer and a second layer. A material of the first layer is different from the material of the second layer.

A bulk acoustic wave resonator includes a substrate, a support layer disposed on the substrate, the support layer including a cavity having a polygon shape with more than three sides in a plane crossing a first direction from the substrate to the support layer, a piezoelectric layer disposed on the support layer, a bottom electrode disposed below the piezoelectric layer, partially overlapping the cavity, and extending across a first side of the cavity, and a top electrode disposed above the piezoelectric layer, partially overlapping the cavity, and extending across a second side of the cavity. The bulk acoustic wave resonator further includes at least one release hole formed in the piezoelectric layer and overlapping a portion of the cavity.

A BAW resonator includes: a piezoelectric film array, including multiple piezoelectric films between a substrate of a chip and a capping layer on the top, where multiple first cavities are provided between adjacent piezoelectric films in a vertical direction, between the piezoelectric films and the capping layer, and between the piezoelectric films and the substrate, second cavities are shared between adjacent piezoelectric films in a first direction in a horizontal plane, and third cavities are shared between adjacent piezoelectric films in a second direction in the horizontal plane; multiple electrode layers, covering at least the top surface and bottom surface of each of the piezoelectric films; and multiple electrode interconnection layers, connected to the electrode layers on the bottom surfaces of the piezoelectric films along sidewalls of the third cavities.

A vibration element includes a vibrating part, and a support part which is coupled to the vibrating part to support the vibrating part, wherein the vibrating part and the support part have a first surface and a second surface having a front and back relationship with the first surface, a first electrode is disposed on the first surface, the first electrode includes a first layer as a foundation layer, and a second layer as an upper layer of the first layer, when performing zoning into a first area where the first electrode is not disposed, a second area where the first layer and the second layer are stacked on one another, and a third area where the first layer is formed, identification symbols formed of two or more of the first to third areas are disposed, and an identification code formed of a plurality of the identification symbols is provided.

A bulk acoustic wave (BAW) structure includes a single crystal piezoelectric material layer, a first electrode, a second electrode and an acoustic reflector. The first and second electrodes are respectively located on a first surface and a second surface of the single crystal piezoelectric material layer. The area of the second electrode is greater than or equal to that of the second surface of the single crystal piezoelectric material layer, and the contact area of the single crystal piezoelectric material layer with the second electrode is equal to the area of the second surface of the single crystal piezoelectric material layer. The acoustic reflector is disposed on a surface of the first electrode.

An RF filter system including a plurality of BAW resonators arranged in a circuit, the circuit including a serial configuration of resonators and a parallel shunt configuration of resonators, the circuit having a circuit response corresponding to the serial configuration and the parallel configuration of the plurality of bulk acoustic wave resonators including a transmission loss from a pass band having a bandwidth from 5.855 GHz to 5.925 GHz. Resonators include a support member with a multilayer reflector structure; a first electrode including tungsten; a piezoelectric film including aluminum scandium nitride; a second electrode including tungsten; and a passivation layer including silicon nitride. At least one resonator includes at least a portion of the first electrode located within a cavity region defined by a surface of the support member.

A wearable ultrasonic device constantly emitting waves attached with a readout display device includes a frame defining a space, an ultrasonic sensor, and a display panel received in the space. The ultrasonic sensor monitors a user's health. The display panel is positioned on the ultrasonic sensor. The ultrasonic sensor includes a signal transmitting layer configured to emit ultrasonic waves. The signal transmitting layer includes a second electrode layer and a plurality of piezoelectric units formed on the second electrode layer. Each piezoelectric unit includes a second piezoelectric material layer formed on the second electrode layer and a conductive layer formed on the second piezoelectric material layer.

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.

An acoustic wave device includes a piezoelectric layer and a pair of electrodes. In a cross-section including first and second directions, at least one electrode of the pair of electrodes includes top, bottom, first side, and second side surfaces, the bottom surface being opposed to the top surface and closer to the piezoelectric layer than the top surface. A first angle between the first side surface and the first main surface is different from a second angle between the second side surface and the first main surface, and at least one of the first angle and the second angle is about 80° or larger.