A bulk acoustic wave resonator and a formation method thereof are provided. The method for forming the bulk acoustic wave resonator includes forming a sacrificial structure on a substrate. A seed layer is formed on the sacrificial structure. A bottom electrode is formed on the seed layer. A piezoelectric layer is formed on the bottom electrode. A top electrode is formed on the piezoelectric layer. The sacrificial structure is removed to form a cavity. The seed layer is etched through the cavity.

In bulk acoustic wave (BAW) resonators having convex surfaces, 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 in the IC package, the BAW resonator including a piezoelectric layer having a convex surface.

A bulk acoustic resonator operable in a bulk acoustic mode includes a resonator body mounted to a separate carrier that is not part of the resonator body. The resonator body includes a piezoelectric layer, a device layer, and a top conductive layer on the piezoelectric layer opposite the device layer. A surface of the device layer opposite the piezoelectric layer is for mounting the resonator body to the carrier.

An acoustic resonator device includes a substrate and a piezoelectric plate. A first portion of the piezoelectric plate is on the substrate. A second portion of the piezoelectric forms a diaphragm suspended over a cavity in the substrate. An interdigital transducer (IDT) is on a surface of the piezoelectric plate, the IDT including first and second busbars on the first portion and interleaved IDT fingers on the diaphragm. A plurality of tethers support the diaphragm over the cavity, each tether providing an electrical connection between a corresponding one of the interleaved IDT fingers and one of the first and second busbars.

An electronic device includes a pop-up device configured to be inserted into a main body of the electronic device in an inserted state, including a gas sensor including a sensor block for sensing a gas, and configured to expose the sensor block to an outer portion of the electronic device in a pop-up state; a power supplier arranged on an outer portion of the pop-up device, configured to supply electric power to the gas sensor; and a connection controller configured to control a connection state of the pop-up device, to block supply of electric power to the gas sensor when the pop-up device is in the inserted state and to supply electric power to the gas sensor when the pop-up device is in the pop-up state, including one or more terminals formed on the pop-up device that move together with the pop-up device when the pop-up device moves.

A radio frequency duplexer comprises a transmit filter including a first plurality of acoustic wave resonators, and a receive filter including a second plurality of acoustic wave resonators. The transmit filter exhibits a transmit insertion loss curve that partially overlaps with a receive insertion loss curve of the receive filter, a frequency range of the overlap of the transmit insertion loss curve and receive insertion loss curve defining a frequency range of crossover of the duplexer. At least one of the first plurality of acoustic wave resonators or the second plurality of acoustic wave resonators include a structure configured to generate a spurious signal at a frequency within the frequency range of the crossover to reduce an amplitude of an interference signal within the frequency range of the crossover.

A bulk acoustic resonator operable in a bulk acoustic mode includes a resonator body mounted to a separate carrier that is not part of the resonator body. The resonator body includes a piezoelectric layer, a device layer, and a top conductive layer on the piezoelectric layer opposite the device layer. The piezoelectric layer is a single crystal of LiNbO.sub.3 cut at an angle of 130°±30°. A surface of the device layer opposite the piezoelectric layer is for mounting the resonator body to the carrier.

A quartz crystal resonator unit that includes: a quartz crystal resonator including an excitation electrode and a connection electrode electrically connected to the excitation electrode; a base member including an electrode pad; an electrically conductive holding member that connects the connection electrode and the electrode pad to each other; and a lid member attached to the base member so as to form an internal space between the lid member and the base member in which the quartz crystal resonator is accommodated. The electrically conductive holding member is a cured product of an electrically conductive adhesive containing (1) a silicone resin as a main component and (2) an epoxy compound having two or more epoxy groups.

A bulk acoustic resonator operable in a bulk acoustic mode includes a resonator body mounted to a separate carrier that is not part of the resonator body. The resonator body includes a piezoelectric layer, a device layer, and a top conductive layer on the piezoelectric layer opposite the device layer. A surface of the device layer opposite the piezoelectric layer is for mounting the resonator body to the carrier.

A micro-acoustic device comprises a confinement structure (CS) adapted to block propagation of acoustic waves of an acoustic wave resonator (TEL, PL, BEL; ES) at an operation frequency of the device to confine the acoustic waves to the acoustic path or the acoustic volume. It is proposed to use a phononic crystal material for producing the confinement structure.