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 thin-film bulk acoustic resonator (FBAR) apparatus includes a lower dielectric layer including a first cavity; an upper dielectric layer including a second cavity, wherein the upper dielectric layer is on the lower dielectric layer; and an acoustic resonance film that is positioned between and separating the first and the second cavities. The acoustic resonance film includes a lower electrode layer, an upper electrode layer, and a piezoelectric film that is sandwiched between the lower and upper electrode layers. A plan view of the first and the second cavities overlap to form an overlapped region having a polygonal shape without parallel sides.

A filter includes n series resonators, one or more parallel resonators, a first inductor between a first terminal and a first of the n series resonators, and a second inductor between an n-th series resonator and a second terminal. Where a resonant frequency of the first series resonator is referred to as a first resonant frequency, a resonant frequency of each of the series resonators other than the first series resonator and the n-th series resonator is referred to as a second resonant frequency, and a resonant frequency of the n-th series resonator is referred to as a third resonant frequency, the first resonant frequency and the third resonant frequency are each higher than the second resonant frequency.

A method for manufacturing a semiconductor apparatus includes: on a base substrate, forming an isolation trench layer, a first dielectric layer, a first metal connecting layer, a piezoelectric film, and an upper electrode layer; forming an acoustic resonance film by patternizing the piezoelectric film, the upper electrode layer, and the first metal connecting layer; above the base substrate, forming a second dielectric layer and a third dielectric layer; forming a first cavity through the third and second dielectric layers, and the protection layer; removing a part of the base substrate to expose the isolation trench layer; forming a fourth dielectric layer under the isolation trench layer; and forming a second cavity through the fourth dielectric layer, the isolation trench layer, and the first dielectric layer, plan views of the first and second cavities forming an overlapped region having a polygon shape without parallel sides.

A method for fabricating bulk acoustic wave resonator with mass adjustment structure, comprising following steps of: forming a sacrificial structure mesa on a substrate; etching the sacrificial structure mesa such that any two adjacent parts have different heights, a top surface of a highest part of the sacrificial structure mesa is coincident with a mesa top extending plane; forming an insulating layer on the sacrificial structure mesa and the substrate; polishing the insulating layer to form a polished surface; forming a bulk acoustic wave resonance structure including a top electrode, a piezoelectric layer and a bottom electrode on the polished surface; etching the sacrificial structure mesa to form a cavity; the insulating layer between the polished surface and the mesa top extending plane forms a frequency tuning structure, the insulating layer between the mesa top extending plane and the cavity forms a mass adjustment structure.

Techniques are disclosed for forming high frequency film bulk acoustic resonator (FBAR) devices that include a bottom electrode formed of a two-dimensional electron gas (2DEG). The disclosed FBAR devices may be implemented with various group III-nitride (III-N) materials, and in some cases, the 2DEG may be formed at a heterojunction of two epitaxial layers each formed of III-N materials, such as a gallium nitride (GaN) layer and an aluminum nitride (AlN) layer. The 2DEG bottom electrode may be able to achieve similar or increased carrier transport as compared to an FBAR device having a bottom electrode formed of metal. Additionally, in some embodiments where AlN is used as the piezoelectric material for the FBAR device, the AlN may be epitaxially grown which may provide increased performance as compared to piezoelectric material that is deposited by traditional sputtering techniques.

A method for forming cavity of bulk acoustic wave resonator comprising following steps of: forming a sacrificial epitaxial structure mesa on a compound semiconductor substrate; forming an insulating layer on the sacrificial epitaxial structure mesa and the compound semiconductor substrate; polishing the insulating layer by a chemical-mechanical planarization process to form a polished surface; forming a bulk acoustic wave resonance structure on the polished surface, which comprises following steps of: forming a bottom electrode layer on the polished surface; forming a piezoelectric layer on the bottom electrode layer; and forming a top electrode layer on the piezoelectric layer, wherein the bulk acoustic wave resonance structure is located above the sacrificial epitaxial structure mesa; and etching the sacrificial epitaxial structure mesa to form a cavity, wherein the cavity is located under the bulk acoustic wave resonance structure.

An FBAR filter device comprising an array of resonators, each resonator comprising a single crystal piezoelectric layer sandwiched between a first and a second metal electrode, wherein the first electrode is supported by a support membrane over an air cavity, the air cavity being embedded in a silicon dioxide layer over a silicon handle, with through-silicon via holes through the silicon handle and into the air cavity, the side walls of said air cavity in the silicon dioxide layer being defined by barriers of a material that is resistant to silicon oxide etchants, and wherein the interface between the support membrane and the first electrode is smooth and flat.

A method for fabricating bulk acoustic wave resonator with mass adjustment structure, comprising following steps of: forming a sacrificial structure mesa on a substrate; etching the sacrificial structure mesa such that any two adjacent parts have different heights, a top surface of a highest part of the sacrificial structure mesa is coincident with a mesa top extending plane; forming an insulating layer on the sacrificial structure mesa and the substrate; polishing the insulating layer to form a polished surface; forming a bulk acoustic wave resonance structure including a top electrode, a piezoelectric layer and a bottom electrode on the polished surface; etching the sacrificial structure mesa to form a cavity; the insulating layer between the polished surface and the mesa top extending plane forms a frequency tuning structure, the insulating layer between the mesa top extending plane and the cavity forms a mass adjustment structure.

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