A method of manufacturing a bulk acoustic wave (BAW) resonator according to an embodiment of the present invention may include: forming a lower electrode above a substrate; forming a nitrogen layer on an upper surface of the lower electrode through nitrogen (N.sub.2) plasma surface treatment; forming a piezoelectric layer made of an AlScN material above the nitrogen layer to align an upper surface of the piezoelectric layer to an N polarity; and forming an upper electrode above the piezoelectric layer aligned to the N polarity.

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 thin-film bulk acoustic resonator (FBAR) apparatus includes a lower dielectric layer including a first cavity; an upper dielectric layer including a second cavity, wherein the upper dielectric layer is on the lower dielectric layer; and an acoustic resonance film that is positioned between and separating the first and the second cavities. The acoustic resonance film includes a lower electrode layer, an upper electrode layer, and a piezoelectric film that is sandwiched between the lower and upper electrode layers. A plan view of the first and the second cavities overlap to form an overlapped region having a polygonal shape without parallel sides.

An acoustic wave resonator for use in a device for wireless communications includes a first electrode, a second electrode, and a piezoelectric layer disposed between the first electrode and the second electrode. The first electrode has a first region made of a material having a first density, and a second region formed as a loop region surrounding the first region and electrically connected to the first region. The second region is made of a material having a second density that is different from the first density.

There is provided a laminated substrate having a piezoelectric film, including: a substrate; and a piezoelectric film provided on the substrate interposing a base film, wherein the piezoelectric film has an alkali niobium oxide based perovskite structure represented by a composition formula of (K.sub.1-xNa.sub.x)NbO.sub.3 (0<x<1) and preferentially oriented in (001) plane direction, and a sound speed of the piezoelectric film is 5100 m/s or more.

A multilayer structure and a piezoelectric device using the same, which have satisfactory crystal orientation even in the submicron region of the thickness of a piezoelectric layer, are provided. The multilayer structure includes a first wurtzite thin film, a first hexagonal metal layer, a first electrode layer, a second hexagonal metal layer, and a second wurtzite thin film stacked in this order. The first electrode layer is formed of a metallic material having an acoustic impedance higher than that of the second wurtzite thin film.

A film bulk acoustic wave resonator (FBAR) is disclosed with recessed and raised frame portions in the piezoelectric film. The FBAR can include a substrate, the piezoelectric film supported to oscillate in a direction opposite to a main surface of the substrate, and a pair of top and bottom electrodes formed respectively on top and bottom surfaces of the film. The recessed frame portion and the raised frame portion can be formed in the film to extend adjacent to each other along a periphery of an active region of the film oscillating during an operation of the film on a top surface of the top electrode.

A thin film piezoelectric acoustic wave resonator and a manufacturing method therefor, and a filter. The film piezoelectric acoustic wave resonator includes: a first base, a first electrode, a piezoelectric plate body, a second electrode and an isolation cavity, wherein the first electrode, the piezoelectric plate body and the second electrode are arranged on a first surface of the first base and are stacked sequentially from top to bottom; the first electrode, the piezoelectric plate body and the second electrode are provided with an overlapping region in a direction perpendicular to the surface of the piezoelectric plate body; in the overlapping region, a gap is formed between the piezoelectric plate body and the first electrode; the isolation cavity surrounds the periphery of the piezoelectric plate body; and the gap communicates with the isolation cavity.

Diplexers, filter devices, and methods are disclosed. A diplexer includes a first chip comprising series resonators of a high band filter, a second chip comprising shunt resonators of the high band filter and series resonators of a low band filters, and a third chip comprising shunt resonators of the low band filter. The series resonators and the shunt resonators of the high band filter are decoupled transversely-excited film bulk acoustic resonators (DXBARs). The series resonators and the shunt resonators of the low band filter are transversely-excited film bulk acoustic resonators (XBARs).

Aspects of acoustic resonators and methods of manufacture of acoustic resonators are described, including acoustic resonators with thinner layers of piezoelectric material. In one example, a method of manufacturing an acoustic resonator includes providing a substrate, depositing a layer of piezoelectric material over the substrate by atomic layer deposition (ALD), and forming an electrode in contact with the layer of piezoelectric material. ALD is used to deposit highly uniform and conformal thin films of piezoelectric material and, in some cases, electrodes and encapsulation layers. The acoustic resonators described herein are better suited for the demands of new radio frequency (RF) filters, duplexers, transformers, and other components in front-end radio electronics and other applications.