Acoustic resonator including extended cavity

A bulk acoustic wave (BAW) resonator, comprising:

• a substrate formed of a nonlinear material;
• an interposer layer over the substrate, the interposer layer being formed of a linear material and a cavity being formed in the interposer layer;
• an acoustic stack over the interposer layer and the cavity, the acoustic stack comprising:
• a bottom electrode;
• a piezoelectric layer over the bottom electrode;
• and
• a top electrode over the piezoelectric layer, wherein an active region of the acoustic stack comprises overlapping portions of the cavity, the bottom electrode, the piezoelectric layer and the top electrode;
• and
• a connecting strip extending from a portion of the top electrode for providing electrical excitation of the acoustic stack, wherein an electric field (E-field) is generated in the BAW resonator, the E-field beginning at the top electrode and terminating at the bottom electrode, in response to the electrical excitation, a portion of the E-field outside the active region of the acoustic stack being a parasitic E-field,
• wherein a thickness of the interposer layer, between the bottom electrode and the substrate, is sufficiently large on a side of the acoustic stack from which the connecting strip extends from the top electrode to substantially prevent the parasitic E-field from passing through the substrate, resulting in a negligible amount of the parasitic E-field passing through the substrate, such that a nonlinear response to the parasitic E-field by the substrate is improved and electrical loss generated in the substrate is reduced.

A bulk acoustic wave (BAW) resonator, comprising:

• a substrate defining a cavity, the substrate being formed of a nonlinear material;
• and
• an acoustic stack over the substrate and the cavity, the acoustic stack comprising:
• a bottom electrode layer;
• a piezoelectric layer over the bottom electrode layer;
• and
• a top electrode layer over the piezoelectric layer, wherein an active region of the acoustic stack comprises overlapping portions of the cavity, the bottom electrode layer, the piezoelectric layer and the top electrode layer, and the top electrode layer includes a connecting strip extending from at least a portion of the top electrode layer in the active region, the connecting strip providing electrical excitation of the acoustic stack, wherein an electric field (E-field) is generated in the BAW resonator in response to the electrical excitation,
• wherein the cavity includes a first extended portion extending from an outer perimeter of the active region underneath the connecting strip, the first extended portion having a length substantially preventing any portion of the E-field outside the active region of the acoustic stack from passing through the substrate, such that a nonlinear response to the E-field by the substrate is improved and electrical loss generated in the substrate is reduced.

A bulk acoustic wave (BAW) resonator device including a plurality of BAW resonators with a shared top electrode connection, the BAW resonator device comprising:

• a substrate defining a cavity, the substrate being formed of a nonlinear material;
• and
• a plurality of acoustic stacks over the substrate and the cavity, the plurality of acoustic stacks comprising:
• a plurality of bottom electrodes corresponding to the plurality of acoustic stacks;
• a piezoelectric layer over the plurality of bottom electrodes;
• and
• a top electrode layer over the piezoelectric layer, wherein active regions of the acoustic stacks comprise overlapping portions of the cavity, the bottom electrodes, the piezoelectric layer and the top electrode layer, respectively, and the top electrode layer includes a plurality of connecting strips extending from at least a portion of the top electrode layer in the active regions, the connecting strips providing corresponding electrical excitations of the acoustic stacks, respectively, wherein electric fields (E-fields) are generated in the BAW resonators in response to the corresponding electrical excitations,
• wherein the E-fields begin at the top electrode layer and terminate at a corresponding one of the bottom electrodes in response to the electrical excitations, respectively, portions of the E-fields outside the active regions of the acoustic stacks being parasitic E-fields,
• wherein the cavity includes inner portions in the active regions of the acoustic stacks, respectively, and a shared extended portion between outer perimeters of the active regions underneath the connecting strips, the shared extended portion containing an electrically insulating material, the electrically insulating material providing a more linear response to any portions of the parasitic E-fields passing through the electrically insulating material than any portions of the parasitic E-fields passing through the substrate, and
• wherein a length of the shared extended portion of the cavity is sufficient to substantially prevent the parasitic E-fields from passing through the substrate.