A filter device includes a first filter chip including a first signal terminal and a second filter chip including a second signal terminal that are mounted above a package substrate including a substrate main body. First and second signal electrode pads are provided on a first main surface of the package substrate and are respectively joined to the first and second signal terminals. First and second outer terminals are provided on a second main surface of the substrate main body. The first and second signal electrode pads and the first and second outer terminals are connected to each other with first and second wirings, respectively. The second outer terminal is located at the first signal electrode pad side and the first outer terminal is located at the second signal electrode pad side when seen from above.

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.

An acoustic wave component is disclosed. The acoustic wave component can include a bulk acoustic wave resonator and a surface acoustic wave device. The bulk acoustic wave resonator can include a first portion of a ceramic substrate, a first piezoelectric layer positioned on the ceramic substrate, and electrodes positioned on opposing sides of the first piezoelectric layer. The surface acoustic wave device can include a second portion of the ceramic substrate, a second piezoelectric layer positioned on the ceramic substrate, and an interdigital transducer electrode on the second piezoelectric layer.

An acoustic wave component is disclosed. The acoustic wave component can include a bulk acoustic wave resonator and a surface acoustic wave device. The bulk acoustic wave resonator can include a first portion of a glass substrate, a first piezoelectric layer positioned on the glass substrate, and electrodes positioned on opposing sides of the first piezoelectric layer. The surface acoustic wave device can include a second portion of the glass substrate, a second piezoelectric layer positioned on the glass substrate, and an interdigital transducer electrode on the second piezoelectric layer.

A bulk acoustic wave resonator is disclosed. The bulk acoustic wave resonator can include a ceramic substrate, and a piezoelectric layer on the ceramic substrate. The bulk acoustic wave resonator can also include first and second electrodes positioned on opposing sides of the piezoelectric layer. The bulk acoustic wave resonator can also include passivation layers that includes a first passivation layer and a second passivation layer. The first passivation layer can be positioned between the ceramic substrate and the first electrode. The second electrode can be positioned between the piezoelectric layer and the second passivation layer. The bulk acoustic wave resonator can further include a frame structure along an edge of an active region of the bulk acoustic wave resonator.

A filter circuit that secures the steepness from a pass range to an attenuation range while maintaining a wide-band transmission characteristic and a filter device including this filter circuit are formed. A filter circuit includes a first filter and a second filter. The first filter is a filter including an LC circuit in which a first frequency band is a pass band and a frequency band not higher than the first frequency band is an attenuation band. The second filter is a filter that attenuates a second frequency band within the first frequency band by using an attenuation pole produced by a resonance or an antiresonance of an acoustic wave resonator. Further, the first filter is placed closer to an antenna terminal than the second filter.

An acoustic wave device includes: a first substrate having a first surface on which an acoustic wave element is located; a second substrate having a second surface on which a functional element is located; a third substrate having a third surface, which faces the first and second surfaces, and a fourth surface being opposite to the third surface, a first metal layer separated from the acoustic wave element and a wiring line in the first substrate and connecting the first and third surfaces; a second metal layer separated from the functional element and a wiring line in the second substrate and connecting the second and third surfaces; a first metal pattern located on the third surface, being in contact with the first and second metal layers, and connecting the first and second metal layers; and a terminal located on the fourth surface and electrically connectable to the first metal pattern.

A multiplexer includes filters and a common terminal connected to an antenna element by a connection path, a first inductance element being connected between the connection path and a reference terminal. A terminal closer to the antenna element among an input terminal and an output terminal of one filter among the filters is connected to a parallel resonator and is connected to the common terminal with a second inductance element interposed therebetween. A terminal closer to the antenna element among an input terminal and an output terminal of each of other filters other than the one filter among the filters is connected to the common terminal and a series resonator.

In a multiplexer, input or output terminals of four acoustic wave filters are connected to, among a plurality of terminals provided on piezoelectric substrates, antenna terminals connected to an antenna connection terminal; the four acoustic wave filters include a first acoustic wave filter and a second acoustic wave filter that is located at a farther position from the antenna connection terminal than a position of the first acoustic wave filter in a plan view of a substrate; and among the plurality of terminals, the terminals located at the closest position to the antenna connection terminal in the plan view of the substrate are connected to the second acoustic wave filter as the antenna terminals.

An electronic component includes: a first substrate; a second substrate that includes a functional element formed on a lower surface of the second substrate, the second substrate being mounted on the first substrate so that the functional element faces an upper surface of the first substrate across an air gap; and an insulating film that is located on the upper surface of the first substrate, overlaps with at least a part of the functional element in plan view, faces the functional element across the air gap, and has a film thickness that is more than half of a distance between a lower surface of the functional element and the upper surface of the first substrate.