A piezoelectric structure is disclosed which includes a single crystal having piezoelectric coefficients d.sub.31 and d.sub.32 of opposite magnitude, such that when an alternating electric field is applied in the Z direction, the piezoelectric structure expands in one of the X and Y directions and contracts in the other of the X and Y direction, a first electrode coupled to the single crystal, and a second electrode coupled to the single crystal, wherein the alternating electric field is input to the single crystal through the first and second electrodes.

Piston mode Lamb wave resonators are disclosed. A piston mode Lamb wave resonator can include a piezoelectric layer, such as an aluminum nitride layer, and an interdigital transducer on the piezoelectric layer. The piston mode Lamb wave resonator has an active region and a border region, in which the border region has a velocity with a lower magnitude than a velocity of the active region. The border region can suppress a transverse mode.

This present disclosure provides a bulk acoustic wave resonator and a bulk acoustic wave filter, and relates to the technical field of filters. A substrate and a piezoelectric stack structure arranged on the substrate are included. The piezoelectric stack structure includes a bottom electrode, a piezoelectric material layer and a top electrode which are sequentially stacked, and an outline of an orthographic projection of the top electrode on the substrate includes at least one Bezier curve of order greater than or equal to 2. Accordingly, a length of a transverse propagation path of transverse acoustic waves can be increased, thereby increasing losses of the transverse acoustic waves during propagation, and reducing influences of the transverse acoustic waves on a transverse parasitic mode caused by the bulk acoustic wave resonator, and namely, an effect of restraining the transverse parasitic mode is improved by the bulk acoustic wave resonator, thereby improving performance of the bulk acoustic wave filter.

An electrode structure of a resonator and a fabrication method for the electrode structure of the resonator are provided. The electrode structure includes a piezoelectric layer. An electrode metal layer, a dielectric layer, a protrusion/frame metal layer and an etching passivation layer are sequentially arranged above the piezoelectric layer. An air gap is formed between the dielectric layer and the protrusion/frame metal layer, and the air gap is located at an electrode edge. Through the air gap between the dielectric layer and the protrusion/frame metal layer above the piezoelectric layer, an electrode protrusion/frame structure of the resonator with an edge air gap is formed, which serves as an electrode part. When the resonator is working, through the air gap, a transverse sound wave can be reflected back to the resonator and be bound in a resonator body. This greatly increases the Q factor and working performance of the resonator.

Acoustic resonators, filters, and methods. An acoustic resonator includes a substrate, a piezoelectric plate, and a diaphragm including a portion of the piezoelectric plate spanning a cavity in a substrate. An interdigital transducer (IDT) on a front surface of the piezoelectric plate includes first and second sets of interleaved interdigital transducer (IDT) fingers extending from first and second busbars respectively. The interleaved IDT fingers extend onto the diaphragm. Overlapping portions of the interleaved IDT fingers define an aperture of the acoustic resonator. First and second dielectric strips are on the front surface of the piezoelectric plate. Each dielectric strip has a first portion under the IDT fingers in a respective margin of the aperture and a second portion extending into a gap between the respective margin and the respective busbar.

A resonator, a filter and a duplexer, which relate to the technical field of resonators. The resonator includes: a substrate, and a lower electrode layer, a piezoelectric layer and an upper electrode layer, which are sequentially formed on the substrate, wherein an acoustic reflection structure is formed on a surface of the substrate that is close to the lower electrode layer, and an overlapping region of the acoustic reflection structure, the lower electrode layer, the piezoelectric layer and the upper electrode layer along a stacking direction forms a resonant region; and in the resonant region, the surface, which is away from the substrate, of at least one of the lower electrode layer, the piezoelectric layer and the upper electrode layer is etched to form an etched region, the depth of the etched region is less than the thickness of an etched layer, and the area of the etched region is less than the area of the resonant region. By means of controlling an etching area ratio of the resonant region to the etched region, the resonator can obtain a plurality of different resonant frequencies on the same wafer without increasing processes.

Provided are a bulk acoustic resonator and a filter. The bulk acoustic resonator includes a substrate having a cavity, and a bottom electrode, a piezoelectric layer and a top electrode that are sequentially arranged on the substrate, where an overlapping area of orthographic projections of the bottom electrode, the piezoelectric layer and the top electrode on the substrate forms a resonance area; and in the resonance area, an outline shape of the orthographic projection of each of the bottom electrode and the top electrode on the substrate is a closed figure formed by connecting M arcs end to end, and the closed figure is an axisymmetric figure, where M is an integer greater than or equal to 2, and the arcs include a concave arc that is concave toward a center of the resonance area and a convex arc that is convex away from the center of the resonance area.

A BAW resonator with an improved lateral energy confinement is provided. The resonator has a bottom electrode in a bottom electrode layer, a top electrode in a top electrode layer and a piezoelectric layer between the bottom electrode layer and the top electrode layer. The piezoelectric layer comprises piezoelectric materials of different piezoelectric polarities.

A transducer structure for a surface acoustic device comprises a composite substrate comprising a piezoelectric layer, a pair of inter-digitated comb electrodes, comprising a plurality of electrode means with a pitch p satisfying the Bragg condition, wherein the inter-digitated comb electrodes are embedded in the piezoelectric layer such that, in use, the excitation of a wave propagating mode in the volume of the electrode means is taking place and is the predominant propagating mode of the structure. The present disclosure relates also to an acoustic wave device comprising at least one transducer structure as described above and to a method for fabricating the transducer structure. The present disclosure relates also to the use of the frequency of the bulk wave propagating in the electrode means of the transducer structure in an acoustic wave device to generate contribution at high frequency, in particular, above 3 GHz.

Disclosed is a Bulk Acoustic Wave (BAW) filter structure with a conductive bridge forming an electrical loop with an electrode for reduced electrical losses. In exemplary aspects disclosed herein, the BAW filter structure includes a transducer with electrodes, a piezoelectric layer between the electrodes, and at least one conductive bridge offset from at least a portion of one of the electrodes by an insulating volume. The conductive bridge forms a first electrical loop between a medial end and a distal end of the electrode. Such a configuration reduces electrical resistance, heat resistance, and/or ohmic losses for improved electrical loss of the BAW filter structure.