A filter includes first and second signal terminals, a filter circuit connected between the first and second signal terminals, a substrate having first and second surfaces, the first and second signal terminals being located on the first surface, a part of the filter circuit being located at a side of the second surface, a line located closer to the first surface than the filter circuit in the substrate, a first end of the line being connected to one of the first and second signal terminals, and a ground terminal that is located on the first surface and to which a second end of the line is connected, an area of a region where the line overlaps with the ground terminal being greater than an area of a region where the line overlaps with the one of the first and second signal terminals when the substrate is viewed in plan view.

A surface acoustic wave (SAW) device includes a piezoelectric substrate, an interdigital transducer (IDT) electrode located on an upper surface of the piezoelectric substrate, a cover covering the upper surface of the piezoelectric substrate from above the IDT electrode, at least one first via conductor extending through at least part of the cover from the upper surface of the piezoelectric substrate to an upper surface of the cover, at least one second via conductor located, on the piezoelectric substrate, inward from the first via conductor in a plan view, extending through at least part of the cover from the upper surface of the piezoelectric substrate to the upper surface of the cover, and having a smaller diameter than the first via conductor, and a conductive layer located on the upper surface of the cover and extending over an upper end of the second via conductor.

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.

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.

A communications module includes a module substrate composed of a plurality of insulating layers, a plurality of wiring layers, and a plurality of wiring vias; and a filter module disposed on the module substrate. At least one of the wiring layers overlaps the filter module in a thickness direction of the module substrate and is connected to a ground potential to function as a ground layer, and an entirety of at least one of the wiring layers and at least one of the wiring vias disposed in a first region in the thickness direction of the module substrate between the filter module and the ground layer are electrically connected to the filter module.

An electric device comprises a substrate (SU) as a carrier and at least two chip components mounted thereto. In the top surface of the substrate a recess (RC) is formed. One or more chip component (BC) is mounted to the bottom surface of the recess referred to as buried chip component. One or more top chip component (TC) is mounted to the top surface of the substrate to cover at least to some extend the recess and the buried chip component. Device pads (PD) are arranged on the bottom surface of the substrate. Each of them is electrically interconnected with one or both of the chip components.

An integrated radio frequency (RF) circuit combines complementary features of passive devices and acoustic filters and includes a first die, a second die, and a third die. The first die includes a substrate having one or more passive devices. The second die includes a first acoustic filter. The second die is stacked and coupled to a first surface of the first die. The third die includes a second acoustic filter. The third die is stacked and coupled to a second surface opposite the first surface of the first die.

A multiplexer includes a common terminal, a first band pass filter that is connected to the common terminal and has a first pass band, and a second band pass filter that is connected to the common terminal and has a second pass band located at higher frequencies than the first pass band. The first band pass filter includes an acoustic wave device that includes a support substrate, a piezoelectric body stacked on the support substrate, and an IDT electrode provided on the piezoelectric body. The piezoelectric body is made of lithium niobate. The acoustic wave device utilizes Rayleigh waves.

A multiplexer includes: first and second substrates overlapping with each other with an air gap interposed therebetween; a first filter disposed on the first substrate and including first series resonators connected in series with a first path, and first parallel resonators; and a second filter disposed on the second substrate and including second series resonators connected in series with a second path, and second parallel resonators connected between the second path and a ground, each of the second series resonators and the second parallel resonators including a piezoelectric film, a first electrode interposed between the piezoelectric film and the second substrate, a second electrode interposed between the piezoelectric film and the air gap, and a resonance region, in at least one second parallel resonator, the first electrode being coupled to the second path, the second electrode being coupled to the ground, the resonance region overlapping with the first path.

A filter module includes an inductor, a filter including first wiring, and second wiring between the inductor and the first wiring and being a direct-current floating potential. The inductor and the first wiring are magnetically coupled, the inductor and the second wiring are magnetically coupled, and the first wiring and the second wiring are capacitively coupled.