A multiplexer includes a common terminal, a first terminal, a second terminal, a first filter device including acoustic wave resonators including series resonators and parallel resonators, an inductor provided between an acoustic wave resonator and the first terminal, and a second filter device. The first filter device further includes a first ground terminal to which a parallel resonator is electrically connected, a second ground terminal to which the parallel resonators are electrically connected, and a wiring provided between the inductor and an acoustic wave resonator. In the first filter device, the wiring is electrically connected to the first ground terminal, and the first ground terminal is not connected to the second ground terminal.

Provided is a multiplexer that includes a first filter (first transmission filter), a second filter (second reception filter), a third filter (third reception filter), a first inductor, and a second inductor. The first inductor is connected in series with one parallel arm resonator (second parallel arm resonator) of the first filter between the one parallel arm resonator and ground. The second inductor is connected in series with another parallel arm resonator (third parallel arm resonator) of the first filter between the other parallel arm resonator and ground. The first inductor and the second inductor have the same winding direction as each other from the first filter side toward the ground side thereof.

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 13030. A surface of the device layer opposite the piezoelectric layer is for mounting the resonator body to the carrier.

Hybrid filters and more particularly filters having acoustic wave resonators (AWRs) and lumped component (LC) resonators and packages therefor are described. In an example, a packaged filter includes a package substrate, the package substrate having a first side and a second side, the second side opposite the first side. A first acoustic wave resonator (AWR) device is coupled to the package substrate, the first AWR device comprising a resonator. A plurality of inductors is in the package substrate.

A multi-piece wiring substrate includes a matrix substrate including first and second insulating layers, and interconnection substrate regions arranged in a matrix. The matrix substrate includes dividing grooves opposing each other and disposed along boundaries between the interconnection substrate regions, and through-holes penetrating the matrix substrate in a thickness direction at positions where the dividing grooves are disposed. The inner surface conductor gradually decreases in thickness from a thick portion in a middle of the inner surface conductor, to thin portions disposed on a side of a boundary between the first and second insulating layers and on a first main surface side, and includes inclination portions each of which gradually increases in thickness from a boundary between corresponding one of the dividing grooves and the inner surface conductor to an inner surface of the inner surface conductor, in vertical sectional view.

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.

Reduced-size guided-surface acoustic wave (SAW) resonators are disclosed. Guided-SAW resonators can achieve high acoustic coupling and acoustic quality Q, but may have a larger surface area compared with a traditional temperature compensated (TC)-SAW resonator. In an exemplary aspect, a guided-SAW device is fabricated with a metal-insulator-metal (MIM) capacitor to produce a guided-SAW which has the same high Q with a surface area which is the same or less than traditional TC-SAW resonators.

An elastic wave device includes a multilayer film including a piezoelectric thin film laminated on a support substrate. In a region outside a region in which an IDT electrode is provided, the multilayer film is not disposed. A first insulating layer extends from at least a portion of the region to a region on the piezoelectric thin film. A wiring electrode extends to a region on the first insulating layer from a region on the piezoelectric thin film and to extend to a region on a portion of the first insulating layer located in the region. A support layer including a cavity defining a hollow space is provided on the support substrate. The support layer includes, on the wiring electrode, a portion extending from the region to a region above an inner end of the first insulating layer.

A multiplexer (1) includes a plurality of filters connected to a common terminal (110). The multiplexer (1) includes: a low-frequency filter (11L) that is formed of at least one surface acoustic wave resonator arranged between the common terminal (110) and the input/output terminal (120) and has a first pass band; a high-frequency filter (12H) that is connected between the common terminal (110) and the input/output terminal (130) and has a second pass band located at a higher frequency than the first pass band; and a capacitor (C.sub.B1) that is serially arranged in a connection path between the common terminal (110) and the low-frequency filter (11L). The Q value of the capacitor (C.sub.B1) in the second pass band is higher than the Q value in the second pass band of a capacitance obtained by treating the at least one surface acoustic wave resonator of the low-frequency filter (11L) as a capacitance.

RF front end systems or modules with an acoustic wave resonator (AWR) on an interposer substrate are described. In an example, an integrated system includes an active die, the active die comprising a semiconductor substrate having a plurality of active circuits therein. An interposer is also included, the interposer comprising an acoustic wave resonator (AWR). A seal frame couples the active die to the interposer, the seal frame surrounding the acoustic wave resonator and hermetically sealing the acoustic wave resonator between the active die and the interposer.