A crystal oscillator includes an oscillating substrate, a hollow frame, a first electrode, and a second electrode. The oscillating substrate includes a main oscillating region and a thinned region that has a thickness smaller than that of the main oscillating region. The first and second electrodes are disposed on a first surface of the oscillating substrate and a second surface opposite to the first surface, respectively. The hollow frame is disposed on the second surface. The second electrode includes a second electrode portion that has at least one opening in positional correspondence with the thinned region. A method for making the crystal oscillator is also provided herein.

An acoustic wave device is provided comprising a substrate and at least one resonator structure of a first type and at least one resonator structure of a second type mounted on the substrate. The resonator structures of the first type are configured to operate as capacitors and have a first thickness, causing the resonator structures to have a first passband frequency range. The resonator structures of the second type have a second thickness that is different from the first thickness, causing the resonator structures to have a second passband frequency range. A method for forming such an acoustic wave device is also provided. A die comprising such an acoustic wave device, a filter comprising such an acoustic wave device, a radio-frequency module comprising such an acoustic wave device, and a wireless mobile device comprising such an acoustic wave device are also provided.

In at least one embodiment, the electric component comprises a first BAW-resonator (1), a second BAW-resonator (2) electrically connected to the first BAW-resonator and a carrier substrate (3) with a top side (30) on which the BAW-resonators are arranged. The first and the second BAW-resonator each comprise a bottom electrode (11,21) and a top electrode (12,22). The bottom electrodes are in each case located between the carrier substrate and the respective top electrode. A first piezoelectric layer (13) is arranged between the top electrode and the bottom electrode of the first BAW-resonator and laterally protrudes from the first BAW-resonator. The second BAW-resonator is mounted on the first piezoelectric layer in a region laterally next to the first BAW-resonator and comprises a second piezoelectric layer (23) between its top electrode and its bottom electrode. The two piezoelectric layers may have different thickness to realize resonators with different resonance frequencies on the same die.

A resonator, a filter and a duplexer, which relate to the technical field of resonators. The resonator includes: a substrate, and a lower electrode layer, a piezoelectric layer and an upper electrode layer, which are sequentially formed on the substrate, wherein an acoustic reflection structure is formed on a surface of the substrate that is close to the lower electrode layer, and an overlapping region of the acoustic reflection structure, the lower electrode layer, the piezoelectric layer and the upper electrode layer along a stacking direction forms a resonant region; and in the resonant region, the surface, which is away from the substrate, of at least one of the lower electrode layer, the piezoelectric layer and the upper electrode layer is etched to form an etched region, the depth of the etched region is less than the thickness of an etched layer, and the area of the etched region is less than the area of the resonant region. By means of controlling an etching area ratio of the resonant region to the etched region, the resonator can obtain a plurality of different resonant frequencies on the same wafer without increasing processes.

A crystal oscillator includes a piezoelectric substrate, a first electrode, a second electrode, and a support frame. The first electrode includes a first electrode portion disposed on a first surface of the piezoelectric substrate. The second electrode is disposed on a second surface of the piezoelectric substrate opposite to the first surface of the piezoelectric substrate. The support frame is made of a photoresist material, and is disposed on the second surface. The support frame surrounds the second electrode portion. At least a portion of the second extending electrode portion is located outside the support frame. A method for making the crystal oscillator is also provided herein.

A crystal oscillator includes an oscillating substrate, a hollow frame, a first electrode, and a second electrode. The oscillating substrate includes a main oscillating region and a thinned region that has a thickness smaller than that of the main oscillating region. The first and second electrodes are disposed on a first surface of the oscillating substrate and a second surface opposite to the first surface, respectively. The hollow frame is disposed on the second surface. The second electrode includes a second electrode portion that has at least one opening in positional correspondence with the thinned region. A method for making the crystal oscillator is also provided herein.

Aspects of this disclosure relate to a bulk acoustic wave device with a plurality of piezoelectric layers having at least one polarization inversion. The bulk acoustic wave device can include a plurality of stacked piezoelectric layers. The plurality of stacked piezoelectric layers can include a piezoelectric layer formed by atomic layer deposition. The bulk acoustic wave device can excite an overtone mode as a main mode. Related filters, multiplexers, packaged radio frequency modules, radio frequency front ends, wireless communication devices, and methods are disclosed.

A bulk acoustic wave resonator having a central region, an outer region, and a raised frame region between the central region and the outer region is disclosed. The bulk acoustic wave resonator can include a piezoelectric layer and a top electrode over the piezoelectric layer. The top electrode is disposed at least in the central region, the outer region, and the raised frame region, the top electrode including a first layer and a second layer. A material of the first layer is different from the material of the second layer.

A piezoelectric thin film resonator includes: a substrate; a piezoelectric film located on the substrate; lower and upper electrodes facing each other across at least a part of the piezoelectric film; a first insertion layer located between the lower and upper electrodes and located in at least a part of an outer peripheral region within a resonance region in which the lower and upper electrodes face each other across the piezoelectric film, the first insertion layer being not located in a center region of the resonance region; and a second insertion layer located between the lower and upper electrodes and located in at least a part of the outer peripheral region, the second insertion layer being not located in the center region, a position of an edge of the second insertion layer being different from a position of an edge of the first insertion film in the resonance region.

An RF circuit device using modified lattice, lattice, and ladder circuit topologies. The devices can include four resonator devices and four shunt resonator devices. In the ladder topology, the resonator devices are connected in series from an input port to an output port while shunt resonator devices are coupled the nodes between the resonator devices. In the lattice topology, a top and a bottom serial configurations each includes a pair of resonator devices that are coupled to differential input and output ports. A pair of shunt resonators is cross-coupled between each pair of a top serial configuration resonator and a bottom serial configuration resonator. The modified lattice topology adds baluns or inductor devices between top and bottom nodes of the top and bottom serial configurations of the lattice configuration. These topologies may be applied using single crystal or polycrystalline bulk acoustic wave (BAW) resonators.