A BAW resonator (BAWR) with improved power durability and improved heat resistance is provided. The resonator comprises a layer stack with a piezoelectric material (PM) between a bottom electrode (ELI) and a top electrode (EL2) and a shunt path parallel (PCPP) to the layer stack provided to enable an RF signal to bypass the layer stack, e.g. to ground (GND). The shunt path (PCPP) has a temperature dependent conductance with a negative temperature coefficient, NTC, of resistance. When the temperature of the device rises due to high power operation, currents that would otherwise permanently damage the device are shunted to ground or another dedicated terminal by the temperature dependent shunt path. Upon cooling down normal operation is resumed.

A quartz crystal resonator unit that includes a substrate, a lid, and an adhesive member that joins the substrate and the lid to each other to form an enclosure; a quartz crystal resonator disposed in the enclosure; and an adjustment member on the quartz crystal resonator and that includes a material whose volatilization amount per unit time and unit volume increases as humidity increases.

A bulk-acoustic wave resonator is provided. The bulk-acoustic wave resonator comprises a substrate comprising an external connection electrode; a connection layer connected to the external connection electrode and disposed on the substrate; a first electrode disposed to cover at least a portion of the connection layer; a piezoelectric layer disposed to cover at least a portion of the first electrode; and a second electrode disposed to cover at least a portion of the piezoelectric layer. The connection layer may be disposed to surround a cavity and may be connected to the first electrode and the second electrode.

There are disclosed acoustic resonators and radio frequency filter devices. An acoustic resonator includes a piezoelectric plate having a front surface. A conductor pattern is formed on the front surface, the conductor pattern including interdigital transducers (IDTs) of one or more pairs of sub-resonators, each pair consisting of two sub-resonators. The two sub-resonators of each pair of sub-resonators are positioned symmetrically about a central axis.

A piezoelectric thin film resonator includes: a substrate; a piezoelectric film located on the substrate; a lower electrode and an upper electrode facing each other across at least a part of the piezoelectric film; and a wiring layer located on the upper electrode, the wiring layer having a thickness equal to or greater than 0.8 m and equal to or less than 3.0 m, at least a part of the wiring layer overlapping in plan view with a resonance region in which the lower electrode and the upper electrode face each other across the piezoelectric film, a distance between an outline of the resonance region and an edge of a lower surface located within the resonance region and farthest from the outline being greater than 0 m and less than 2 m.

A filter device according to an embodiment of the present disclosure includes a first filter and a second filter that are connected in parallel between a first terminal and a second terminal. The first filter includes multiple series arm resonators. The series arm resonators are disposed in series in a path from the first terminal via the first filter to the second terminal. The series arm resonators include a first series arm resonator and a second series arm resonator. Under a condition that a value obtained by dividing a difference between an antiresonance frequency and a resonance frequency of each series arm resonator by the resonance frequency is defined as a fractional bandwidth, a first fractional bandwidth of the first series arm resonator is different from a second fractional bandwidth of the second series arm resonator.

A filter device includes a first filter and a second filter. The first filter and the second filter are disposed in parallel between a first terminal and a second terminal. A first passband of the filter device includes at least part of a second passband of the first filter. The first passband includes at least part of a third passband of the second filter. The second passband is narrower than the first passband. The third passband is narrower than the first passband. The third passband has a center frequency higher than a center frequency of the second passband. The first filter includes multiple elastic wave resonators and a first capacitive element. The first capacitive element is connected in parallel with the first elastic wave resonator.

There are disclosed acoustic resonators and radio frequency filter devices. An acoustic resonator includes a piezoelectric plate having a front surface. A conductor pattern is formed on the front surface, the conductor pattern including interdigital transducers (IDTs) of one or more pairs of sub-resonators, each pair consisting of two sub-resonators. The two sub-resonators of each pair of sub-resonators are positioned symmetrically about a central axis.

A bulk acoustic wave (BAW) resonator includes: a substrate; an acoustic reflector disposed in the substrate; a first electrode disposed over the acoustic reflector; a second electrode; and a piezoelectric layer between the first and second electrodes. The second electrode is not disposed between the first electrode and the acoustic reflector. The BAW resonator further includes a block disposed over the substrate and beneath the piezoelectric layer. A contacting overlap of the acoustic reflector, the first electrode, the second electrode and the piezoelectric layer defines an active area of the BAW resonator.

In a crystal resonator plate (2), a support part (24) extends from only one corner part positioned in the +X direction and in the Z direction of a vibrating part (22) to an external frame part (23) in the Z direction. The vibrating part (22) and at least part of the support part (24) form an etching region (Eg) having a thickness thinner than a thickness of the external frame part (23). A stepped part is formed at a boundary of the etching region (Eg), and a first lead-out wiring (223) is formed over the support part (24) to the external frame part (23) so as to overlap with the stepped part. At least part of the stepped part that is superimposed on the first lead-out wiring (223) is formed so as not to be parallel to the X axis in plan view.