Methods for manufacturing resonator structures and corresponding resonator structures are described. A first wafer including a first piezoelectric material is singulated and bonded to a second wafer.

A piezoelectric thin film resonator includes: a substrate; a piezoelectric film located on the substrate; lower and upper electrodes facing each other across the piezoelectric film; a mass load film that is located at least one of a first side, which is closer to the upper electrode, of the piezoelectric film and a second side, which is closer to the lower electrode, of the piezoelectric film, separated from the upper and lower electrodes, and surrounds in plan view a resonance region at least in part, the lower and upper electrodes facing each other across the piezoelectric film in the resonance region; and an acoustic reflection layer that includes the resonance region and the mass load film in plan view, is located in or on the substrate, and includes an air gap or an acoustic mirror in which at least two layers with different acoustic characteristics are stacked.

Embodiments provide a solidly-mounted bulk acoustic wave (BAW) resonator and method of making same. In embodiments, the BAW resonator may include a planarization portion in an inactive region of the BAW resonator that is coplanar with a piezoelectric layer of the BAW resonator in an active region of the BAW resonator. Other embodiments may be described and claimed.

Disclosed is an acoustic wave resonator comprising a substrate material formed of aluminum nitride (AlN) doped with one or more of beryllium (Be), strontium (Sr), and sodium (Na) to enhance performance of the acoustic wave resonator.

A single crystal film bulk acoustic wave resonator includes a substrate layer, a Bragg reflection layer, a first bonding layer, a second bonding layer, a piezoelectric layer and an electrode layer; a width of the electrode layer is smaller than that of the piezoelectric layer. The resonator further includes a first silicon oxide layer and a second silicon oxide layer, which surround the first bonding layer and the second bonding layer respectively, and a plurality of first air holes horizontally arranged and a plurality of second air holes horizontally arranged are respectively formed in the first silicon oxide layer and the second silicon oxide layer. Each of the plurality of first air holes corresponds to and is communicated with a respective one of the plurality of second air holes. The piezoelectric layer is made of AlN or lithium niobate.

A manufacturing process for a bulk acoustic resonator, comprising: making an acoustic mirror on a substrate; making a bottom electrode layer for covering the acoustic mirror on the substrate; performing chemical treatment on a peripheral part of the bottom electrode layer to form a modified layer, which surrounds the bottom electrode layer; making a piezoelectric layer on the bottom electrode layer; and making a top electrode layer on the piezoelectric layer. A bulk acoustic resonator, comprising: a substrate, an acoustic mirror formed on the substrate, and a bottom electrode layer, a piezoelectric layer and a top electrode layer that are sequentially formed on the substrate with the acoustic mirror, chemical treatment is performed on a part of the bottom electrode layer close to an edge of the acoustic mirror to form a modified layer. Parasitic oscillation of the resonator is inhibited, and wiring of a top electrode is greatly simplified.

An acoustic device includes a piezoelectric layer between a first, bottom electrode and a second, top electrode, and an acoustic mirror optimized for reflecting longitudinal waves and shear waves at a target operating frequency. The acoustic mirror includes lower acoustic impedance layers and at least one higher acoustic impedance layer. In an example, layers of the acoustic mirror alternate between lower impedance and higher impedance, with a first lower acoustic impedance layer adjacent to the bottom electrode, and a first higher acoustic impedance layer having a greater thickness than a second higher acoustic impedance layer. In another example, the acoustic mirror has a higher acoustic impedance layer with a thickness corresponding to at least half of a wavelength of the target operating frequency in the higher acoustic impedance layer. An acoustic device with an acoustic mirror optimized for both longitudinal waves and shear waves reduces energy losses for increased efficiency.

Resonator devices are disclosed. An acoustic resonator device includes a piezoelectric plate having front and back surfaces, an acoustic Bragg reflector on the back surface, and an interdigital transducer (IDT) on the front surface. The acoustic Bragg reflector reflects a primary shear acoustic mode excited by the IDT in the piezoelectric plate over a frequency range including a resonance frequency and an anti-resonance frequency of the acoustic resonator device.

Layer structures for RF filters can be fabricated using rare earth oxides and epitaxial aluminum nitride, and methods for growing the layer structures. A layer structure can include an epitaxial crystalline rare earth oxide (REO) layer over a substrate, a first epitaxial electrode layer over the crystalline REO layer, and an epitaxial piezoelectric layer over the first epitaxial electrode layer. The layer structure can further include a second electrode layer over the epitaxial piezoelectric layer. The first electrode layer can include an epitaxial metal. The epitaxial metal can be single-crystal. The first electrode layer can include one or more of a rare earth pnictide, and a rare earth silicide (RESi).

To improve the Q value of a piezoelectric thin-film element in a state in which unnecessary vibration is suppressed, an acoustic reflection film (104) is affixed to a first electrode (102), a piezoelectric single-crystal substrate (101) is thinned by polishing from the other surface (101b) of the piezoelectric single-crystal substrate (101), such that the first electrode (102) and piezoelectric thin film (105) are piled on the piezoelectric single-crystal substrate (101). In this polishing, a pressure (polishing pressure) to the surface (101b) during polishing in an electrode formation region where the first electrode (102) is formed differs from that in a non-electrode formation region around the electrode formation region. Consequently, the electrode formation region of the piezoelectric thin film (105), where the first electrode (102) is formed, is made thinner than the non-electrode formation region around the electrode formation region.