Embodiments of this disclosure relate to acoustic wave filters configured to filter radio frequency signals. An acoustic wave filter includes a first bulk acoustic wave resonator on a substrate, a second bulk acoustic wave resonator on the substrate, a conductor electrically connecting the first bulk acoustic wave resonator in anti-series with the second bulk acoustic wave resonator, and an air gap positioned between the conductor and a surface of the substrate. The air gap can reduce parasitic capacitance associated with the conductor. Acoustic wave filters disclosed herein can suppress a second harmonic.

An acoustic resonator filter includes a series portion of the acoustic resonator filter, the series portion including at least one series acoustic resonator electrically connected, in series, between first and second ports of the acoustic resonator filter configured to pass a radio-frequency (RF) signal from the first port to the second port, and a shunt portion of the acoustic resonator filter, the shunt portion including a plurality of shunt acoustic resonators electrically connected between one node of the series portion and a ground, where a difference between anti-resonant frequencies of each of the plurality of shunt acoustic resonators is smaller than a difference between resonant frequencies of each of the plurality of shunt acoustic resonators.

An acoustic resonator filter includes a series portion including at least one series acoustic resonator electrically connected, in series, between first and second ports of the acoustic resonator filter configured to pass a radio-frequency (RF) signal from the first port to the second port, a shunt portion including a plurality of shunt acoustic resonators electrically connected to each other, in anti-series, between one node of the series portion and a ground, and a DC voltage terminal configured to generate a DC voltage across at least one of the plurality of shunt acoustic resonators by an electrical connection of the DC voltage terminal to a first electrode of the at least one of the plurality of shunt acoustic resonators and to a different second electrode of the at least one of the plurality of shunt acoustic resonators. A DC voltage may be generated across the at least one series acoustic resonator.

A film bulk acoustic resonator (FBAR) structure includes a bottom cap wafer, a piezoelectric layer disposed on the bottom cap wafer, the piezoelectric layer including a single crystalline piezoelectric material, a bottom electrode disposed below the piezoelectric layer; a top electrode disposed above the piezoelectric layer; and a cavity disposed below the bottom electrode.

Acoustic resonator devices and filters are disclosed. An acoustic resonator includes a substrate having a trap-rich region adjacent to a surface and a single-crystal piezoelectric plate having parallel front and back surfaces, the back surface attached to the surface of the substrate except for a portion of the piezoelectric plate forming a diaphragm that spans a cavity in the substrate. An interdigital transducer (IDT) is formed on the front surface of the single-crystal piezoelectric plate such that interleaved fingers of the IDT are disposed on the diaphragm. The single-crystal piezoelectric plate and the IDT are configured such that a radio frequency signal applied to the IDT excites a shear primary acoustic mode within the diaphragm.

A bulk-acoustic wave resonator includes: a substrate; a first electrode disposed on the substrate; a piezoelectric layer disposed to cover at least a portion of the first electrode; a second electrode disposed to cover at least a portion of the piezoelectric layer; a metal pad connected to the first electrode and the second electrode; and a connection member connected an upper surface of the metal pad. A lower end portion of the connection member includes a tapered portion decreasing in a diameter in a direction toward a lower end of the connection member, and an angle between an inclined surface of the tapered portion and the upper surface of the metal pad is 45° to 80°.

A crystal oscillator includes: a crystal resonator plate having a first excitation electrode and a second excitation electrode. A first sealing member covers the first excitation electrode of the crystal resonator plate. A second sealing member covers the second excitation electrode of the crystal resonator plate. An internal space is formed by bonding the first sealing member to the crystal resonator plate and the second sealing member to the crystal resonator plate, and seals a vibrating part of the crystal resonator plate. First and second shield electrodes are connected to a fixed potential (e.g. GND potential) in the internal space.

A bulk-acoustic wave resonator includes: a substrate; a first electrode disposed on the substrate; a piezoelectric layer disposed to cover at least a portion of the first electrode; a second electrode disposed to cover at least a portion of the piezoelectric layer; a metal pad connected to the first electrode and the second electrode; and a connection member connected an upper surface of the metal pad. A lower end portion of the connection member includes a tapered portion decreasing in a diameter in a direction toward a lower end of the connection member, and an angle between an inclined surface of the tapered portion and the upper surface of the metal pad is 45° to 80°.

A piezoelectric component of the present disclosure includes: a substrate having a rectangular plate shape having a longitudinal direction and a width direction; a pair of electrodes disposed on a first surface of the substrate so as to leave space therebetween which is located in a central region in the longitudinal direction of the substrate; and a piezoelectric element both ends of which are fixed to the pair of electrodes, respectively, the pair of electrodes each including a notch extending from a central region side and in the longitudinal direction of the substrate.

The present disclosure provides a film bulk acoustic wave resonator and a preparation method thereof, and relates to the technical field of semiconductors. The film bulk acoustic wave resonator includes a substrate and a bottom electrode, a piezoelectric layer and a top electrode which are located on an upper surface of the substrate, the bottom electrode is provided with a first arched part so as to form a first cavity between the first arched part and the substrate; and a first reflection cavity is formed between the bottom electrode and the piezoelectric layer and located in a slope of the first arched part, the bottom electrode is provided with the first arched part and the first reflection cavity may be located in an oblique plane of the slope of the first arched part.