Embodiments of this disclosure relate to acoustic wave filters configured to filter radio frequency signals. An acoustic wave filter includes a first bulk acoustic wave resonator on a substrate, a second bulk acoustic wave resonator on the substrate, a conductor electrically connecting the first bulk acoustic wave resonator in anti-series with the second bulk acoustic wave resonator, and an air gap positioned between the conductor and a surface of the substrate. The air gap can reduce parasitic capacitance associated with the conductor. Acoustic wave filters disclosed herein can suppress a second harmonic.

Embodiments of this disclosure relate to bulk acoustic wave resonators on a substrate. The bulk acoustic wave resonators include a first bulk acoustic wave resonator, a second bulk acoustic wave resonator, a conductor electrically connecting the first bulk acoustic wave resonator to the second bulk acoustic wave resonator, and an air gap positioned between the conductor and a surface of the substrate.

A filter includes a series-arm resonator located on a path that connects an input/output terminal (11m) with an input/output terminal (11n), and a first parallel-arm resonant circuit connected between a node, which is located on the path, and ground. The first parallel-arm resonant circuit includes a parallel-arm resonator, and a pair of a capacitor and a switch connected in parallel with each other and in series with the parallel-arm resonator between the parallel-arm resonator and ground. An interconnect line (a1) is connected to the input/output terminal (11m), and an interconnect line (a2) is connected to the input/output terminal. The parallel-arm resonator and the switch are connected by an interconnect line (a3). The interconnect line (a3) has a characteristic impedance lower than a characteristic impedance of the interconnect line (a1) or a characteristic impedance of the interconnect line (a2).

A method for the batch production of acoustic wave filters comprises: synthesizing N theoretical filters, each filter defined by a set of j theoretical resonator(s) having a triplet C.sub.0ij,eq, .sub.rij,eq and .sub.aij,eq, these parameters grouped into subsets; determining a reference resonator structure for each subset, naturally having a resonant frequency .sub.r,ref, where .sub.aij,eq<.sub.r,ref<.sub.rij,eq; determining, for each theoretical resonator, an elementary building block comprising an intermediate resonator R.sub.ij, a parallel reactance Xp.sub.ij and/or a series reactance Xs.sub.ij, the intermediate resonator R.sub.ij having a triplet C.sub.0ij, .sub.r,ref and .sub.a,ref, the parameters C.sub.0ij, Xpij and/or Xs.sub.ij defined so the elementary building block has a triplet: C.sub.0ij,eq, .sub.rij,eq and .sub.aij,eq; determining the geometrical dimensions of the actual resonators R.sub.ij of the filters so they have a capacitance C.sub.0ij; producing each actual resonator; associating series and/or parallel reactances with actual resonators in order to form the elementary building blocks.

Bulk acoustic wave (BAW) resonators, and particularly shaped border (BO) rings for BAW resonators are disclosed. Top electrode arrangements are disclosed that include a BO ring arranged about a periphery of a top electrode, where the BO ring forms a top surface having a shape that is sloped or graded in comparison to planar surfaces of the top electrode. The top surface of the BO ring may be arranged such that a height of the top surface is graded in a descending manner toward a central region of the BAW resonator. BAW resonators as disclosed herein are provided with high quality factors and suppression of spurious modes while also providing reduced acoustic leakage and mode conversion.

An acoustic device includes a foundation structure and a transducer provided over the foundation structure. The foundation structure includes a piezoelectric layer between a top electrode and a bottom electrode. The piezoelectric layer has an active portion within an active region of the transducer, and a bi-polar border portion within a border region of the transducer. The piezoelectric material in the active portion has a first polarization. The bi-polar border portion has a first sub-portion and a second sub-portion, which resides either above or below the first sub-portion. The piezoelectric material in the first sub-portion has the first polarization, and the piezoelectric material in the second sub-portion has a second polarization, which is opposite the first polarization.

An electronic package includes a first substrate and a second substrate disposed beneath the first substrate. The electronic package also includes a perimeter wall extending between an inner surface of the first substrate and an opposing inner surface of the second substrate to provide separation between the first substrate and the second substrate. A cavity exists between opposing inner surfaces of the first substrate and the second substrate. A first filter comprising a first plurality of bulk acoustic wave (BAW) resonators disposed over the inner surface first substrate. The electronic package also includes a second filter comprising a second plurality of BAW resonators disposed over the second substrate

A filter includes a series-arm resonator located on a path that connects an input/output terminal (11m) with an input/output terminal (11n), and a first parallel-arm resonant circuit connected between a node, which is located on the path, and ground. The first parallel-arm resonant circuit includes a parallel-arm resonator, and a pair of a capacitor and a switch connected in parallel with each other and in series with the parallel-arm resonator between the parallel-arm resonator and ground. An interconnect line (a1) is connected to the input/output terminal (11m), and an interconnect line (a2) is connected to the input/output terminal. The parallel-arm resonator and the switch are connected by an interconnect line (a3). The interconnect line (a3) has a characteristic impedance lower than a characteristic impedance of the interconnect line (a1) or a characteristic impedance of the interconnect line (a2).

A piezoelectric vibrator that includes a piezoelectric film with a pair of electrodes disposed on opposing sides of the piezoelectric film. Moreover, the vibrator includes first and second adjustment films with the first adjustment film covering the first surface of the piezoelectric film in a first region and the second adjustment film covering the first surface of the piezoelectric film in a second region that is different from the first region. Moreover, the second region of the piezoelectric film has a greater displacement than the first region when the piezoelectric vibrator vibrates.

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.