Disclosed is an air gap type film bulk acoustic resonator (FBAR). The air gap type FBAR includes a substrate which includes an air gap portion in a top surface thereof, a lower electrode formed on the substrate, a piezoelectric layer formed on the lower electrode, and an upper electrode formed on the piezoelectric layer. Here, the lower electrode includes a first lower electrode formed spaced apart from the air gap portion in the substrate and a second lower electrode formed on the substrate to be separated from the first lower electrode by being stacked to surround only a part of a top of the air gap portion in order to form a non-deposition area of the air gap portion.

An acoustic wave device includes a first substrate, a piezoelectric layer including one main surface facing the first substrate and another main surface facing a direction opposite to the one main surface, a functional electrode on at least one of the one and the other main surfaces, and a second substrate including a first main surface facing the other main surface of the piezoelectric layer, a second main surface facing a direction opposite to the first main surface, and a through-hole penetrating from the first main surface to the second main surface. An angle at which a side surface of the through-hole is inclined from the second main surface toward the first main surface is equal to or more than about 0? and equal to or less than about 5? based on a normal line with respect to the second main surface.

Techniques for improving acoustic wave devices are disclosed, including filters, oscillators and systems that may include such devices. A first piezoelectric layer having a piezoelectrically excitable resonance mode may be provided. A second piezoelectric layer may also be provided. The first piezoelectric layer and the second piezoelectric layer may have respective thicknesses so that the acoustic wave device has a resonant frequency. A temperature compensating layer may be included. A substrate may be provided.

An acoustic wave device includes an acoustic wave element including a support including a support substrate having a thickness in a first direction, a piezoelectric layer laminated on the support portion and including a first main surface and a second main surface opposite to the first main surface in the first direction, and a functional electrode on at least one of the first main surface and the second main surface of the piezoelectric layer, and a package to house the acoustic wave element. The support portion includes a first space on a piezoelectric layer side at a position where the first space at least partially overlaps the functional electrode in a plan view in the first direction, the package includes a second space outside the first space, and the piezoelectric layer includes a through-hole communicating with the first space and the second space.

A micro-electro-mechanical system (MEMS) device includes a substrate having a cavity and a MEMS structure disposed over the cavity and attached to the substrate. The MEMS structure includes at least one first piezoelectric layer having a first piezoelectric coefficient and two second piezoelectric layers respectively disposed under and above the first piezoelectric layer, where each second piezoelectric layer has a second piezoelectric coefficient higher than the first piezoelectric coefficient. The MEMS structure further includes a first electrode layer and a second electrode layer sandwiching the two second piezoelectric layers.

A piezoelectric MEMS resonator is provided. The resonator comprises a single crystal silicon microstructure suspended over a buried cavity created in a silicon substrate and a piezoelectric resonance structure located on the microstructure. The resonator is designed and fabricated based on porous silicon related technologies including selective formation and etching of porous silicon in silicon substrate, porous silicon as scarified material for surface micromachining and porous silicon as substrate for single crystal silicon epitaxial growth. All these porous silicon related technologies are compatible with CMOS technologies and can be conducted in a standard CMOS technologies platform.

A bulk-acoustic wave resonator includes a substrate; a lower electrode formed on the substrate, and at least a portion of the lower electrode is formed on a cavity; a piezoelectric layer formed on the lower electrode; an upper electrode formed on the piezoelectric layer; a membrane layer formed below the lower electrode and forming the cavity together with the substrate; and a protruding portion formed on the membrane layer and further formed in the cavity in a direction that extends away from the membrane layer.

A lower electrode and an adhesive layer made of an insulator are formed on a back surface on the ion implantation layer side of a piezoelectric single crystal substrate. A supporting substrate in which sacrificial layers made of a conductive material have been formed is bonded to the surface of the adhesive layer. By heating the composite body including the piezoelectric single crystal substrate, the lower electrode, the adhesive layer, and the supporting substrate, a layer of the piezoelectric single crystal substrate is detached to form a piezoelectric thin film. A liquid polarizing upper electrode is formed on a detaching interface of the piezoelectric thin film. A pulsed electric field is applied using the polarizing upper electrode and the sacrificial layers as counter electrodes. Consequently, the piezoelectric thin film is polarized.

A front end module (FEM) for a 5.6 GHz Wi-Fi acoustic wave resonator RF filter circuit. The device can include a power amplifier (PA), a 5.6 GHz resonator, and a diversity switch. The device can further include a low noise amplifier (LNA). The PA is electrically coupled to an input node and can be configured to a DC power detector or an RF power detector. The resonator can be configured between the PA and the diversity switch, or between the diversity switch and an antenna. The LNA may be configured to the diversity switch or be electrically isolated from the switch. Another 5.6 GHZ resonator may be configured between the diversity switch and the LNA. In a specific example, this device integrates a 5.6 GHz PA, a 5.6 GHZ bulk acoustic wave (BAW) RF filter, a single pole two throw (SP2T) switch, and a bypassable LNA into a single device.

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.