Switchable and/or tunable filters, methods of manufacture and design structures are disclosed herein. The method of forming the filters includes forming at least one piezoelectric filter structure comprising a plurality of electrodes formed to be in contact with at least one piezoelectric substrate. The method further includes forming a micro-electro-mechanical structure (MEMS) comprising a MEMS beam in which, upon actuation, the MEMS beam will turn on the at least one piezoelectric filter structure by interleaving electrodes in contact with the piezoelectric substrate or sandwiching the at least one piezoelectric substrate between the electrodes.

An acoustic waveguide having high-Q resonator characteristics is disclosed and a fabrication method is described. Various waveguide-based test-vehicles, implemented in single crystal silicon and transduced by thin aluminum nitride films, are demonstrated. Silicon resonators with type-I and type-II dispersion characteristics are presented to experimentally justify the analytical mode synthesis technique for realization of high quality-factor silicon Lamb wave resonators. An analytical design procedure is also presented for geometrical engineering of the waveguides to realize high-Q resonators without the need for geometrical suspension through narrow tethers or rigid anchors. The effectiveness of the dispersion engineering methodology is verified through development of experimental test-vehicles in 20 μm-thick single-crystal silicon (SCS) waveguides with 500 nm aluminum nitride transducers.

An acoustic wave filter device includes a lower electrode disposed between a substrate and a piezoelectric layer, an upper electrode disposed on the piezoelectric layer, and an insulating layer disposed on the upper electrode. The insulating layer exposes portions of the upper electrode.

An acoustic wave device includes: a support substrate; a first piezoelectric substrate bonded to a first principal surface of the support substrate, the first piezoelectric substrate being a single crystal substrate, a first acoustic wave resonator located on an opposite surface of the first piezoelectric substrate from a surface to which the support substrate is bonded, the first acoustic wave resonator including an IDT; a second piezoelectric substrate bonded to a second principal surface of the support substrate opposite from the first principal surface, the second piezoelectric substrate being a single crystal substrate; and a second acoustic wave resonator located on an opposite surface of the second piezoelectric substrate from a surface to which the support substrate is bonded, the second acoustic wave resonator including an IDT.

A BAW resonator filter can include a BAW resonator pass-band filter ladder, the BAW resonator pass-band filter ladder can be configured to pass frequency components of an input signal in a pass-band of frequencies received at an input node of the BAW resonator pass-band filter ladder to an output node of the BAW resonator pass-band filter ladder. A first rejection-band series resonator can be coupled in series between an input port of the BAW resonator pass-band filter ladder and the input node, the first rejection-band series resonator can have a first anti-resonant frequency peak in a rejection-band of frequencies that is less than the pass-band of frequencies. A second rejection-band series resonator can be coupled in series between an output port of the BAW resonator filter and the output node, the second rejection-band series resonator can have a second anti-resonant frequency peak in the rejection-band of frequencies.

Techniques are disclosed for forming high frequency film bulk acoustic resonator (FBAR) devices having multiple resonator thicknesses on a common substrate. A piezoelectric stack is formed in an STI trench and overgrown onto the STI material. In some cases, the piezoelectric stack can include epitaxially grown AlN. In some cases, the piezoelectric stack can include single crystal (epitaxial) AlN in combination with polycrystalline (e.g., sputtered) AlN. The piezoelectric stack thus forms a central portion having a first resonator thickness and end wings extending from the central portion having a different resonator thickness. Each wing may also have different thicknesses. Thus, multiple resonator thicknesses can be achieved on a common substrate, and hence, multiple resonant frequencies on that same substrate. The end wings can have metal electrodes formed thereon, and the central portion can have a plurality of IDT electrodes patterned thereon.

Acoustic wave devices are disclosed. An acoustic wave device can include a first filter and a second filter coupled to a common node. The second filter includes acoustic wave resonators of a first type (e.g., bulk acoustic wave resonators) and a series acoustic wave resonator of the second type (e.g., a surface acoustic wave resonator) that is coupled between the acoustic wave resonators of the first type and the common node. The acoustic wave device can further include a loop circuit coupled to the first filter, in which the loop circuit is configured to generate an anti-phase signal to a target signal at a particular frequency. In certain embodiments, the first filter is a receive filter and the second filter is a transmit filter.

Aspects of this disclosure relate to a hybrid acoustic LC filter cascaded with a non-acoustic LC filter. The hybrid acoustic filter can filter a radio frequency signal. The hybrid acoustic LC filter can include acoustic resonators, an inductor, and a capacitor. The inductor and capacitor can be external to an acoustic resonator die. The non-acoustic LC filter includes an LC circuit. Related multiplexers, wireless communication devices, and methods are disclosed.

In accordance with an embodiment, an RF system includes a transmit path having a first tunable transmit band stop filter, and a power amplifier coupled to an output of the first tunable transmit band stop filter, where the first tunable transmit band stop filter is configured reject a receive frequency and pass a transmit frequency; a receive path comprising an LNA; and a duplex filter having a transmit path port coupled to an output of the power amplifier, a receive path port coupled to an input of the LNA, and an antenna port, where the duplex filter is configured to pass the transmit frequency and reject the receive frequency between the antenna port and the transmit path port, pass the receive frequency and reject the transmit frequency between the antenna port and the receive path port.

An acoustic wave filter includes a substrate having voids formed therein; a first resonator disposed on one or more of the voids, and a second resonator disposed on other of the voids. A first trimming layer is provided in the first resonator, and a second trimming layer is provided in the second resonator. The second trimming layer is formed of a material having an etching rate for a given etchant different from that of the first trimming layer.