Bulk acoustic wave resonator and method of fabricating same

An acoustic wave resonator, comprising:

• (a) a substrate having a top surface;
• (b) an acoustic mirror formed on the top surface of the substrate or in the substrate, having a first edge and an opposite, second edge;
• (c) a first dielectric layer formed on the substrate such that the dielectric layer is substantially in contact with the first and second edges of the acoustic mirror;
• (d) a first electrode formed over the substrate and overlying the acoustic mirror, having a first end portion and an opposite, second end portion, wherein at least one of the first and second end portions extends beyond one of the first and second edges of the acoustic mirror and is situated on the first dielectric layer;
• (e) a second dielectric layer formed on the acoustic mirror and the first dielectric layer such that the second dielectric layer is substantially in contact with the first and second end portions of the first electrode;
• (f) a piezoelectric layer formed on the first electrode and the second dielectric layer such that the piezoelectric layer overlapping the end portion of the first electrode is isolated from the first electrode;
• and
• (g) a second electrode deposited on the piezoelectric layer having a portion situated above the acoustic mirror.

An acoustic wave resonator comprising:

• (a) a substrate having a top surface;
• (b) an acoustic mirror formed on the top surface of the substrate or in the substrate, having a first edge and an opposite, second edge;
• (c) a dielectric layer formed on the substrate such that the dielectric layer is substantially in contact with the first and second edges of the acoustic mirror;
• (d) a first electrode formed over the substrate and overlying the acoustic mirror, having a first end portion and an opposite, second end portion, wherein the first end portion extends beyond one of the first and second edges of the acoustic mirror and situates on the dielectric layer and the second end portion locates between the first and second edges of the acoustic mirror;
• (e) a piezoelectric layer formed on the first electrode and extending beyond the second end portion of the first electrode and onto the dielectric layer so as to define an air gap therebetween;
• and
• (f) a second electrode deposited on the piezoelectric layer having a portion situated above the acoustic mirror and extending crossover the second end portion of the first electrode.

An acoustic wave resonator, comprising:

• (a) a substrate having a top surface;
• (b) an acoustic mirror formed on the top surface of the substrate or in the substrate, having a first edge and an opposite, second edge;
• (c) a first electrode formed on the acoustic mirror, having a end portion;
• (d) a piezoelectric layer formed on the first electrode;
• and
• (e) a second electrode formed on the piezoelectric layer,
• wherein at least one of the first electrode and the second electrode and the piezoelectric layer define an air gap in a region that overlaps the end portion of the first electrode.

A method of fabricating an acoustic wave resonator, comprising the steps of:

• (a) forming an acoustic mirror having a first edge and an opposite, second edge, on a top surface of a substrate or in the substrate;
• (b) forming a dielectric layer on the substrate such that the dielectric layer is substantially in contact with the first and second edges of the acoustic mirror;
• (c) forming a first electrode having a end portion, over the acoustic mirror, the end portion extending beyond the acoustic mirror and onto the dielectric layer;
• (d) forming a piezoelectric layer on the first electrode and the dielectric layer;
• and
• (e) forming a second electrode on the piezoelectric layer such that the second electrode extends beyond the end portion of the first electrode to define a region in which the second electrode overlapping the end portion of the first electrode is isolated from the piezoelectric layer.

A method of fabricating an acoustic wave resonator, comprising the steps of:

• (a) forming an acoustic mirror having a first edge and an opposite, second edge, on a top surface of a substrate or in the substrate;
• (b) forming a dielectric layer on the substrate such that the dielectric layer is substantially in contact with the first and second edges of the acoustic mirror;
• (c) forming a first electrode having a first end portion and an opposite, second end portion, over the acoustic mirror, wherein the first end portion extends beyond the first edge of the acoustic mirror and onto the dielectric layer and wherein the second end portion extends beyond the second edge of the acoustic mirror or locates between the first and second edges of the acoustic mirror;
• (d) forming a piezoelectric layer on the first electrode and extending beyond at least one of the first and second end portions of the first electrode and crossover the first electrode layer so as to define a region in which the piezoelectric layer crossover the first electrode layer is isolated from the first electrode layer;
• and
• (e) forming a second electrode deposited on the piezoelectric layer having a portion situated above the acoustic mirror and extending crossover at least one of the first and second end portions of the first electrode and the defined region.