An acoustic resonator includes a substrate, a center portion, an extending portion, and a barrier layer. A first electrode, a piezoelectric layer, and a second electrode are sequentially stacked on the substrate in the central portion. The extending portion is configured to extend from the center portion, and includes an insertion layer disposed below the piezoelectric layer. The barrier layer is disposed between the first electrode and the piezoelectric layer.

A piezoelectric thin film resonator includes: a substrate; lower and upper electrodes located on the substrate; a piezoelectric film that has a lower piezoelectric film mainly composed of aluminum nitride and an upper piezoelectric film mainly composed of aluminum nitride, the lower piezoelectric film and the upper piezoelectric film being in contact with each other in at least a part of a resonance region where the lower electrode and the upper electrode face each other across at least a part of the piezoelectric film, and a fluorine concentration at a boundary face with which the lower piezoelectric film and the upper piezoelectric film are in contact being 0.03 atomic % or less; and an insulating film that is located between the lower piezoelectric film and the upper piezoelectric film in a region other than the at least a part of the resonance region and contains silicon oxide.

A piezoelectric thin film resonator includes: a substrate; a lower electrode located on the substrate through an air gap; a piezoelectric film located so as to have a resonance region where the lower electrode and an upper electrode face each other across the piezoelectric film and having a lower piezoelectric film and an upper piezoelectric film, in an extraction region where the lower electrode is extracted from the resonance region, a lower end of a first end face of the lower piezoelectric film being substantially aligned with or located further out than an outer periphery of the air gap, a second end face of the upper piezoelectric film being inclined, an upper end of the second end face being substantially aligned with or located further in than the outer periphery, the lower piezoelectric film having a substantially uniform film thickness between the first end face and the second end face.

Bulk acoustic wave (BAW) resonators having convex surfaces, and methods of forming the same are disclosed. An example BAW resonator includes a first electrode, a piezoelectric layer formed on the first electrode, the piezoelectric layer having a convex surface, and a second electrode formed on the convex surface. An example integrated circuit (IC) package includes a BAW resonator disposed in the IC package, the BAW resonator including a piezoelectric layer having a convex surface.

An aluminum nitride film contains a Group IV element and a Group II or Group XII element, and an atomic composition ratio of the Group II or Group XII element to the Group IV element is less than 1.

A filter is provided that includes resonators connected in series between first and second ports. Each of the resonators includes a piezoelectric layer; and an interdigital transducer (IDT) having a plurality of interleaved fingers at a surface of the piezoelectric layer. The piezoelectric layer and the IDT are configured such that a radio frequency signal applied to the IDT excites a primary shear acoustic mode in the piezoelectric layer. The filter includes a capacitor connected between ground and a node between the first bulk acoustic resonator and the second bulk acoustic resonator.

A BAW resonance device, comprising: a first electrode layer, the first electrode layer comprising a first sub-layer and a second sub-layer; a piezoelectric layer, the first electrode layer being located at a first side of the piezoelectric layer; a second electrode layer, located at a second side of the piezoelectric layer, the second electrode layer comprising a third sub-layer and a fourth sub-layer, and a region where the first sub-layer, the third sub-layer, and the piezoelectric layer overlap being a resonance region; a first passive structure, in contact with at least one edge of the first sub-layer; and a second passive structure, in contact with at least one edge of the third sub-layer. The first passive structure comprises: a first raised portion, located in the resonance region; a first passivation portion, located between the first raised portion and the first electrode layer; and a first extension portion.

The present disclosure provides a bulk acoustic wave (BAW) filter structure and a preparation method thereof. According to the present disclosure, piezoelectric film elements are formed on a surface of an epitaxial substrate to form a transfer structure; resonant regions are defined on a supporting substrate and covered with bonding units to obtain a bonding structure; upper and lower surfaces of the transfer structure are reversed, and bottom electrode units are bonded to the resonant regions correspondingly one to one to obtain a BAW structure; and the epitaxial substrate is removed, and top electrode units are formed on surfaces of the piezoelectric film elements that are in contact with the epitaxial substrate previously. The BAW filter structure of the present disclosure can achieve batch production with low cost, high efficiency and high yield.

Disclosed is a method for manufacturing a piezoelectric Al.sub.xGa.sub.1-xN (0.5?x?1) thin film, comprising: forming a stress control layer comprised of a Group III nitride on a silicon substrate by chemical vapor deposition (CVD); and depositing a piezoelectric Al.sub.xGa.sub.1-xN (0.5?x?1) thin film on the stress control layer, the thin film being deposited by PVD at 0.3 Tm (Tm is melting temperature of a piezoelectric thin film material) or higher. Further, a method for manufacturing a device in conjunction with piezoelectric Al.sub.xGa.sub.1-xN (0.5?x?1) thin films is provided.

A bulk acoustic resonator, a method for manufacturing a bulk acoustic resonator, a filter, and an electronic device are provided. The bulk acoustic resonator includes a substrate, an acoustic reflection structure, a bottom electrode, a piezoelectric layer and a top electrode. The acoustic reflection structure, the bottom electrode, the piezoelectric layer and the top electrode are arranged sequentially in a direction away from the substrate. A first depression is defined on a surface of the bottom electrode away from the substrate. In forming the piezoelectric layer on a side of the bottom electrode away from the substrate, morphology of the first depression is transferred to a surface of the piezoelectric layer away from the substrate to form a second depression on a surface of the piezoelectric layer away from the substrate. The piezoelectric layer has an equal thickness.