Bulk acoustic wave resonator

Abstract

The present disclosure relates to bulk acoustic wave resonators. An example bulk acoustic wave (BAW) resonator includes a first electrode; a second electrode; a piezoelectric layer disposed between the first electrode and the second electrode; a substrate having the first electrode, the second electrode, and the piezoelectric layer disposed thereon, the second electrode disposed between the substrate and the piezoelectric layer; an active region comprising an overlapping area of the first electrode, the piezoelectric layer, and the second electrode; and a frame disposed on the piezoelectric layer, surrounding the active region; wherein the piezoelectric layer has a first thickness in the active region and a second thickness under the frame, the second thickness being different from the first thickness.

Description

Technical Field

[0001] This disclosure generally relates to wireless communication devices, and more particularly to bulk acoustic wave (BAW) resonators. Background Technology

[0002] Electrical resonators are used in modern electronic devices. For example, in wireless communication devices, radio frequency (RF) resonators can be used in filters, such as filters with electrically connected series and shunt resonators, forming trapezoidal and lattice structures. Filters can be included in circuitry connected between the antenna and the transceiver to filter the received and transmitted signals.

[0003] Various types of filters utilize mechanical resonators, such as bulk acoustic wave (BAW) resonators (including thin-film bulk acoustic resonators (FBARs) and solid-state mounted resonators (SMRs)) or surface acoustic wave (SAW) resonators. Resonators convert electrical signals into mechanical signals (e.g., vibrations) and mechanical signals into electrical signals. For example, a BAW resonator is an acoustic device comprising a stack of layers of piezoelectric material that may be included between two electrodes. Sound waves can resonate across the acoustic stack, where the resonant frequency of the wave is determined by the materials in the acoustic stack and the thickness of each layer (e.g., piezoelectric layer and electrode layer). One type of BAW resonator may include a piezoelectric thin film as the piezoelectric material, which may be called an FBAR, as described above. FBARs can resonate at GHz frequencies and are therefore relatively small, for example, having a thickness of approximately several micrometers and length and width dimensions of several hundred micrometers. BAW resonators, such as FBARs, are susceptible to acoustic losses. Acoustic losses can adversely affect the performance and reliability of the resonators and filters used in the implementation. Therefore, it is desirable to mitigate acoustic losses in resonators (e.g., resonators used in filters in electronic devices). Summary of the Invention

[0004] In some embodiments, a bulk acoustic wave (BAW) resonator may include a first electrode, a second electrode, and a piezoelectric layer disposed between the first electrode and the second electrode. The BAW resonator may include a substrate on which the first electrode, the second electrode, and the piezoelectric layer are disposed. The second electrode may be disposed between the substrate and the piezoelectric layer. The BAW resonator may include an active region comprising an overlapping area of ​​the first electrode, the piezoelectric layer, and the second electrode. The BAW resonator may include a frame disposed on the piezoelectric layer and surrounding the active region. The piezoelectric layer may have a first thickness in the active region and a second thickness below the frame, the second thickness being different from the first thickness.

[0005] In some embodiments, an integrated circuit (IC) may include a substrate having a first electrode layer, a second electrode layer, and a piezoelectric layer. The IC may include a first bulk acoustic wave (BAW) resonator including a first active region and a first frame. The first active region may include a first overlapping region of the first electrode layer, the piezoelectric layer, and the second electrode layer. The first frame may be disposed on the piezoelectric layer and surround the first active region. The IC may include a second BAW resonator including a second active region and a second frame. The second active region may include a second overlapping region of the first electrode layer, the piezoelectric layer, and the second electrode layer. The second frame may be disposed on the piezoelectric layer and surround the second active region. The piezoelectric layer may have a first thickness in the first and second active regions and a second thickness below the first and second frames, the second thickness being different from the first thickness.

[0006] In some embodiments, a device may include a first circuit and an electrical filter coupled to the first circuit. The electrical filter may include a bulk acoustic wave (BAW) resonator. The BAW resonator may include a first electrode, a second electrode, and a piezoelectric layer disposed between the first electrode and the second electrode. The BAW resonator may include a substrate on which the first electrode, the second electrode, and the piezoelectric layer are disposed. The second electrode may be disposed between the substrate and the piezoelectric layer. The BAW resonator may include an active region comprising an overlapping area of ​​the first electrode, the piezoelectric layer, and the second electrode. The BAW resonator may include a frame disposed on the piezoelectric layer and surrounding the active region. The piezoelectric layer may have a first thickness in the active region and a second thickness below the frame, the second thickness being different from the first thickness. Attached Figure Description

[0007] Figure 1A This is a block diagram of a device in which a BAW resonator can be used according to some embodiments.

[0008] Figure 1B This is a schematic diagram depicting an electrical filter in which a BAW resonator can be used according to some embodiments.

[0009] Figure 2 This is a block diagram depicting a BAW resonator according to some embodiments.

[0010] Figure 3A This is a top view of a BAW resonator according to some embodiments.

[0011] Figure 3B It is described according to some embodiments Figure 3A The cross-sectional view of the BAW resonator along line 3B-3B.

[0012] Figure 3C It is described according to some embodiments Figures 3A to 3B A side view of the piezoelectric layer of the BAW resonator.

[0013] Figure 4 This is a flowchart depicting a method for forming a BAW resonator according to some embodiments. Detailed Implementation

[0014] Figure 1A This is a block diagram of an apparatus 10 in which a BAW resonator according to some embodiments can be used. Apparatus 10 may include an antenna 12, an electrical filter 14, and a transceiver 16. The antenna may be a device that converts an electrical signal into a radio wave or vice versa. The signal may be any time-varying variable (e.g., voltage, current, charge, electromagnetic waves, etc.). The electrical signal may be a signal conveyed by time-varying electrical parameters (e.g., voltage, current, charge, etc.). The antenna 12 may transmit and receive from a radio transmission medium, which may be a medium configured to carry radio signals (e.g., air). The radio wave or radio signal may be an EM wave in the radio / microwave portion of the electromagnetic (EM) spectrum. The electrical filter may be a device configured to transmit (or amplify) a specific frequency of the electrical signal and block (or attenuate) other frequencies. The transceiver may be a device configured to transmit and receive signals (e.g., electrical signals). The transceiver 16 may couple an electrical signal for transmission through the electrical filter 14 to the antenna 12. Transceiver 16 can receive electrical signals from antenna 12 via electrical filter 14. Electrical filter 14 may include circuitry including BAW resonator 18. The BAW resonator may be an acoustic resonator, wherein mechanical (acoustic) waves can travel through the thickness (bulk volume) of the piezoelectric material of the acoustic resonator. The piezoelectric material may be a dielectric material that enables the conversion between electrical energy and elastic energy. Some embodiments of BAW resonator 18 are described below. Electrical filter 14 and transceiver 16 may be portions of one or more integrated circuits (ICs). The IC may be a device formed on a substrate (e.g., a semiconductor substrate).

[0015] Figure 1BThis is a schematic diagram depicting an electrical filter in which BAW resonators according to some embodiments may be used. Electrical filter 14 may include BAW resonators 181…186. BAW resonator 181 may be coupled between nodes 19 and 20. A node may be a point where two or more circuit elements are connected. A node may be shown in the diagram as a solid dot at the junction of wires. Wires that cross each other but do not have a node or have jumpers are not connected. Note that, for ease of illustration, a node may be shown as two or more separate junctions connected only by wires and without any circuit elements (e.g., short-circuit connections). In this case, the reference number assigned to the node may be at one of the junctions or at one of the wires between the junctions, all of which collectively represent the node. BAW resonator 182 may be coupled between nodes 20 and 22. BAW resonator 183 may be coupled between nodes 22 and 24. BAW resonator 184 may be coupled between nodes 20 and 26. BAW resonator 185 may be coupled between nodes 22 and 26. BAW resonator 186 may be coupled between nodes 24 and 26. Node 26 may be coupled to electrical ground. Electrical ground may be a reference voltage (e.g., 0 V) ​​to which other voltages in the circuit can be compared. Node 19 may be an input to electrical filter 14, and node 24 may be an output to electrical filter 14.

[0016] As shown in detail A, the BAW resonator 18 may include a first electrode 25, a piezoelectric structure 27, and a second electrode 31. The first electrode 25 may be a first terminal 1021 of the BAW resonator 18, and the second electrode 31 may be a second terminal 1022 of the BAW resonator 18. The terminals of the device may be electrical connection points. As shown in detail B, the BAW resonators 181…186 may be electrically coupled via conductive interconnects of the IC 17. The conductive interconnects may be conductive layers 104, separated by dielectric layers 106 formed on the substrate of the IC. The layers may be materials formed on the substrate. The layers may be bonded to the substrate or another layer. The layers may be uniform, for example, uniform surface area, uniform thickness, or both. The layers may be patterned, for example, non-uniform surface area, non-uniform thickness, or both. The layers may be patterned into unconnected portions, for example, electrically isolated portions. The conductive layers may be layers of conductive materials (e.g., metals). The dielectric layer may be a dielectric material layer (e.g., various dielectric materials used in ICs are well known in the art). One or more conductive layers 104 may be patterned to electrically couple the terminals of BAW resonators 181...186 to form nodes 19, 20, 22, 24 and 26.

[0017] Each BAW resonator 181…186 may have a resonant frequency and an anti-resonant frequency. The resonant frequency (also called the resonant frequency) is the frequency at which the resonator has minimum impedance. The anti-resonant frequency (also called the anti-resonant frequency) is the frequency at which the resonator has maximum impedance. The resonant and anti-resonant frequencies can be determined by the construction of the BAW resonator. For example, the frequency at which the BAW resonates can be at least partially determined by the thickness and material properties of its piezoelectric layer. BAW resonators 181…183 may be series resonators between nodes 19 and 24. Series resonators allow the transmission of electrical signals at or near the resonant frequency and block the transmission of electrical signals at or near the anti-resonant frequency. BAW resonators 184…186 may be shunt resonators to node 26. Shunt resonators can operate inversely to series resonators. That is, a shunt resonator can block the transmission of electrical signals at or near the resonant frequency while allowing the transmission of electrical signals at or near the anti-resonant frequency. A combination of a series resonator and a shunt resonator (e.g., BAW resonators 181…186) can provide a frequency band in which electrical signals with frequencies within the band can be transmitted from the input (IN) to the output (OUT) (called the passband), while electrical signals with frequencies outside the band are blocked from being transmitted from the input (IN) to the output (OUT).

[0018] This document describes some embodiments of BAW resonators with constructions that mitigate acoustic losses. Device 10 may be an example type of device in which the BAW resonator according to the embodiments can be used (e.g., a mobile phone or a similar type of device for receiving and transmitting radio waves). However, the BAW resonator according to the embodiments can be used in any type of device with an electrical filter. Figure 1B The bandpass filter is one example type of electrical filter in which a BAW resonator according to an embodiment can be used. The BAW resonator described herein may be a series resonator or a shunt resonator and may be combined with other BAW resonators to form an electrical filter, such as the bandpass filter shown in the examples or any other type of electrical filter known in the art (e.g., a notch filter).

[0019] Figure 2This is a block diagram depicting a BAW resonator 18 according to some embodiments. The BAW resonator 18 may include a first electrode 25, a piezoelectric structure 27, a second electrode 31, and a frame 29. The BAW resonator 18 may also include a substrate 33 on which a layer is formed to dispose of the first electrode 25, the piezoelectric structure 27, the second electrode 31, and the frame 29. In some embodiments, the first electrode 25 may include a first surface and an opposing second surface. The piezoelectric structure 27 may also include a first surface and an opposing second surface. The first surface of the piezoelectric structure 27 may face the second surface of the first electrode 25. The second electrode 31 may also include a first surface and an opposing second surface. The first surface of the second electrode 31 may face the second surface of the piezoelectric structure 27. This arrangement of the first electrode 25, the piezoelectric structure 27, and the second electrode 31 allows the piezoelectric structure 27 to be sandwiched between the first electrode 25 and the second electrode 31.

[0020] The first electrode 25 and the second electrode 31 may be formed of the same or different materials. The electrodes of the device may be conductors through which electricity enters or exits. For example, the first electrode 25 and the second electrode 31 may be formed of one or more conductive materials (e.g., molybdenum (Mo), W, Pt, Ru, Al, Ta, Cu, or similar materials known in the art). The piezoelectric structure 27 may comprise a piezoelectric material (e.g., AlN or similar materials known in the art). The piezoelectric structure may be an arrangement of piezoelectric materials (e.g., portions of a piezoelectric layer formed on a substrate). The frame 29 may be formed of one or more dielectric or metallic materials. The frame of the BAW resonator may be a structure surrounding the active region of the resonator. The active region of the BAW resonator may be a region capable of generating and maintaining acoustic resonance. The active region may be implemented as the overlapping region of the first electrode 25, the piezoelectric structure 27, and the second electrode 31. The frame 29 may be formed on the piezoelectric layer 35 having the piezoelectric structure 27. The region of the piezoelectric layer 35 occupied by the frame 29 may be referred to as the frame region. The frame region may be adjacent to the active region. In some embodiments, the piezoelectric layer 35 may be thinner in the frame region than in the active region, as further discussed below.

[0021] The substrate 33 may be adjacent to the second surface of the second electrode 31. The substrate may be a structure on which layers can be formed. Therefore, in some embodiments, the stack of the first electrode 25, the piezoelectric structure 27, and the second electrode 31 may be supported by the substrate 33. In some embodiments, the substrate 33 may comprise silicon, but other materials such as gallium arsenide (GaAs) and indium phosphide (InP) should be considered.

[0022] The substrate 33 may include an acoustic reflector 28. The acoustic reflector of the BAW resonator may be a structure for acoustically isolating the active region from the substrate. The acoustic reflector 28 may be a cavity formed in the substrate 33 (e.g., an air-filled cavity). Alternatively, the acoustic reflector 28 may be a cavity in the substrate 33 at least partially filled with a material such as an acoustic reflective material known in the art (e.g., alternating layers of high acoustic impedance material and low acoustic impedance material).

[0023] Figures 3A to 3C A view of an IC having a BAW resonator according to some embodiments is shown. Figure 3A This is a top view showing a portion of an IC according to some embodiments. Figure 3B It is described according to some embodiments Figure 3A The cross-sectional view of the IC along line 3B-3B. Figure 3C It is described according to some embodiments Figures 3A to 3B A side view of the piezoelectric layer of the BAW resonator.

[0024] like Figure 3A As shown, the BAW resonator 18A can be formed using a layer on substrate 33. A portion of substrate 33 is shown in... Figure 3A The layer may include a first electrode layer 56, a piezoelectric layer 35, and a second electrode layer 52. Parts of the first electrode layer 56, the piezoelectric layer 35, and the second electrode layer 52 are shown in the figure. Figure 3A The second electrode layer 52 may be disposed between the substrate 33 and the piezoelectric layer 35. The piezoelectric layer 35 may be disposed between the second electrode layer 52 and the first electrode layer 56. The second electrode layer 52 may be patterned to form a second electrode 31. The first electrode layer 56 may be patterned to form a first electrode 25. The piezoelectric layer 35 may be patterned to form a piezoelectric structure 27. The BAW resonator 18A may include a frame 29 that can occupy a frame region 59A on the piezoelectric layer 35 (shown in...). Figure 3B (Middle). The frame region 59A can surround the active region 60A of the BAW resonator 18A. For example... Figures 3B to 3C As shown and discussed below, the piezoelectric layer 35 may be thinner in the frame region 59A than in the active region 60A. Region 61 of the piezoelectric layer 35 may be a region other than the active region 60A and the frame region 59A. In some embodiments, all or a portion of region 61 of the piezoelectric layer 35 may have different thicknesses in the active region 60A and in the frame region 59A.

[0025] like Figure 3BAs shown, the IC may include BAW resonators 18A and 18B. A first electrode layer 56 may be patterned into portions 56A and 56B. Portion 56A of the first electrode layer 56 may be the first electrode 35 of BAW resonator 18A. Portion 56B of the first electrode layer 56 may be the first electrode 35 of BAW resonator 18B. In this example, a second electrode layer 52 may be formed on the substrate 33 and may be used by both BAW resonators 18A and 18B as electrically coupled corresponding second electrodes 31. In other examples, the second electrode layer 52 may be patterned to form separate, non-electrically coupled second electrodes 31 of BAW resonators 18A and 18B. The substrate 33 may include cavities 66A and 66B (e.g., filled with air). Cavities 66A and 66B may be acoustic reflectors 28 of BAW resonators 18A and 18B, respectively. The second electrode layer 52 may overlap the cavities over their entire extent.

[0026] A piezoelectric layer 35 may be formed on the substrate 33 and the second electrode layer 52. The piezoelectric layer 35 may be formed by either BAW resonators 18A or 18B as the corresponding piezoelectric structure 27. In this example, the piezoelectric layer 35 may include a first portion disposed on the substrate 33 and a second portion disposed on the second electrode layer 52. The second electrode layer 52 may include a first portion covered by the piezoelectric layer 35 and a second portion not covered by the piezoelectric layer 35.

[0027] In some embodiments, layer 62 may be formed on piezoelectric layer 35 to form at least a portion of the frame 29 of each BAW resonator 18A and 18B. Layer 62 may be a dielectric material. Layer 62 may be patterned to form frame portions 62A and 62B. Frame portion 62A may be all or part of the frame 29 of BAW resonator 18A, and frame portion 62B may be all or part of the frame 29 of BAW resonator 18B. Frame portion 62A may surround the active region 60A of BAW resonator 18A. Frame portion 62B may surround the active region 60B of BAW resonator 18B. In some embodiments, layer 64 may be formed on piezoelectric layer 35 to form another portion of the frame 29 of each BAW resonator 18A and 18B. Layer 64 may be a dielectric material (e.g., the same as or different from layer 62). Layer 64 may be patterned to form wing portions 64A and wing portions 64B. The flanks of a BAW resonator can be portions of the resonator outside the active region that provide stress relief, energy mitigation, and similar functions known in the art. The flanks can be portions of the frame of the BAW resonator. In this example, flank portion 64A can be disposed on piezoelectric layer 35. A first portion of frame portion 62A can be disposed on flank portion 64A. A second portion of frame portion 62A can be formed on piezoelectric layer 35. Similarly, flank portion 64B can be disposed on piezoelectric layer 35. A first portion of frame portion 62B can be disposed on flank portion 64B. A second portion of frame portion 62B can be formed on piezoelectric layer 35. In other embodiments, flank portions 64A and 64B can be cavities (e.g., filled with air) rather than layers of material.

[0028] The frame portion 62A and the side wing portion 64A of the BAW resonator 18A can occupy the frame region 59A. The frame portion 62B and the side wing portion 64B of the BAW resonator 18B can occupy the frame region 59B. The frame region 59A can surround the active region 60A. The frame region 59B can surround the active region 60B. Figure 3B The portion of the display area 61 excluding the active area and the frame area (e.g., the area between BAW resonators 18A and 18B).

[0029] A portion 56A of the first electrode layer 56 may be formed on the frame portion 62A and the piezoelectric layer 35. A portion 56B of the first electrode layer 56 may be formed on the frame portion 62B and the piezoelectric layer 35. In some embodiments, a portion 56A of the first electrode layer 56, a portion of the piezoelectric layer 35 (e.g., piezoelectric structure 27), and a portion of the second electrode layer 52 are stacked within the active region 60A. Figure 3CAs shown, the piezoelectric layer 35 has a thickness 82 within the active region 60A. The piezoelectric layer 35 has a thickness 80 within the frame region 59A. In some embodiments, the thickness 82 may differ from the thickness 80, for example, being greater than or less than the thickness 80. In some embodiments, the piezoelectric layer 35 may be thinner in the frame region 59A than in the active region 60A. Reducing the thickness of the piezoelectric layer 35 within the frame region 59A can reduce the coupling of parasitic modes and improve acoustic losses across the frame. Additionally, for a given height of BAW resonator, reducing the thickness of the piezoelectric layer 35 within the frame region 59A can allow for thicker layers 62A / 64A. Similarly, a portion 56B of the first electrode layer 56, a portion of the piezoelectric layer 35 (e.g., piezoelectric structure 27), and a portion of the second electrode layer 52 are stacked within the active region 60B. The piezoelectric layer 35 may have a thickness 80 in the frame region 59B and a thickness 82 in the active region 60B.

[0030] Figure 4 This is a flowchart depicting a method 400 for forming a BAW resonator according to some embodiments. Method 400 can be performed using one or more machines used in constructing an IC, which are well known in the art. Method 400 may begin at step 402, where a bottom electrode (e.g., a second electrode 31) may be formed on a substrate. At step 404, a piezoelectric layer may be formed on the substrate and the bottom electrode. At step 406, the piezoelectric layer may be patterned to be thicker in the active region of the BAW resonator and thinner in the frame region. At step 408, a frame may be formed on the piezoelectric layer. The frame may occupy the frame region and may surround the active region. At an optional step 410, side wings (e.g., using a dielectric material or cavity) may be formed in the frame. At step 412, a top electrode (e.g., a first electrode 25) may be formed on the piezoelectric layer and the frame.

[0031] While some processes and methods with various operations may have been described, one or more embodiments also relate to apparatus or devices for performing these operations. The apparatus may be specifically constructed for the desired purpose, or the apparatus may be or include a general-purpose computer selectively activated or configured by a computer program stored in the computer. Various general-purpose machines may be used with computer programs written in accordance with the teachings herein, or it may be more convenient to construct more specialized devices to perform the desired operations.

[0032] As used herein, the phrase “at least one of…” following a list of items (where each item is separated by the terms “and” or “or”) modifies the entire list, not each member of the list (i.e., each item). The phrase “at least one of…” does not require a selection from at least one of every listed item; rather, it allows for the inclusion of at least one of any of the items and / or at least one of any combination of items. By example, the phrases “at least one of A, B, and C” or “at least one of A, B, or C” each refer to only A, only B, or only C; and / or any combination of A, B, and C. In examples where a selection is intended from “at least one of each of A, B, and C” or alternatively “at least one of A, at least one of B, and at least one of C”, this will be explicitly stated.

[0033] As used herein, the term “coupling” and its derivatives include: (a) electrical and communication coupling; and (b) does not imply a direct connection but may include an intermediary element unless described as “direct coupling”.

[0034] Relative terms (such as "above," "below," "top," "bottom," "upper," and "lower") are used to describe the relationships between various elements, as illustrated in the accompanying drawings. In addition to the orientations depicted in the drawings, these relative terms are intended to encompass different orientations of the device and / or elements. For example, if the device is inverted relative to the view in the drawings, then an element described as "above" another element (for example) will now be "below" said element. Similarly, if the device is rotated 90 degrees relative to the view in the drawings… o An element that was described as being “above” or “below” another element will now be more commonly described as being “adjacent” to another element; where “adjacent” means being adjacent to another element or having one or more layers, materials, structures, etc. between the elements.

[0035] As used in the specification and appended claims, and in addition to its ordinary meaning, the term "substantially" also means within the limits or extent acceptable to a person skilled in the art. For example, "substantially identical" means that a person skilled in the art would consider the compared items to be identical. As used in the specification and appended claims, and in addition to its ordinary meaning, the terms "basically" or "substantially" also mean within the acceptable limits or extent. For example, "substantially canceled" means that a person skilled in the art would consider cancellation acceptable.

[0036] Although one or more embodiments of the invention have been described in some detail for clarity of understanding, certain changes may be made within the scope of the claims. Therefore, the described embodiments are intended to be illustrative rather than restrictive, and the scope of the claims is not intended to be limited to the details given herein, but rather to be modified within the scope of the claims and their equivalents. In the claims, elements and / or steps do not imply any particular order of operation unless expressly stated in the claims.

[0037] The boundaries between the components, operations, and data storage devices are, to some extent, arbitrary and are illustrated within the context of a particular illustrative configuration. Other functional arrangements are contemplated and fall within the scope of this invention. Generally, the structure and functionality of individual components presented in the exemplary configuration can be implemented as combined structures or components. Similarly, the structure and functionality presented as a single component can be implemented as a single component. These and other variations, additions, and improvements fall within the scope of the appended claims.

Claims

1. A bulk acoustic wave (BAW) resonator, comprising: First electrode; Second electrode; A piezoelectric layer is disposed between the first electrode and the second electrode; A substrate on which the first electrode, the second electrode and the piezoelectric layer are disposed, wherein the second electrode is disposed between the substrate and the piezoelectric layer; The active region includes the overlapping area of ​​the first electrode, the piezoelectric layer, and the second electrode; as well as A frame, which is disposed on the piezoelectric layer and surrounds the active region; The piezoelectric layer has a first thickness in the active region and a second thickness below the frame, the second thickness being different from the first thickness.

2. The BAW resonator of claim 1, wherein the frame includes side wings, and wherein the piezoelectric layer has the second thickness below the side wings.

3. The BAW resonator according to claim 1, wherein the frame comprises a first material, the first material being a dielectric material or a metal, and a first portion of the first material is disposed on the piezoelectric layer.

4. The BAW resonator of claim 1, wherein the frame is disposed between a first portion of the piezoelectric layer having the second thickness and the first electrode.

5. The BAW resonator of claim 4, wherein the first portion of the piezoelectric layer is disposed between the frame and the second electrode.

6. The BAW resonator of claim 5, wherein a second portion of the piezoelectric layer having the second thickness is disposed outside the perimeter of the second electrode on the substrate, and wherein the frame is disposed on the second portion of the piezoelectric layer.

7. The BAW resonator of claim 6, wherein a third portion of the piezoelectric layer having the second thickness is disposed outside the perimeter of the frame on the substrate.

8. The BAW resonator of claim 1, wherein the substrate includes an acoustic reflector, and wherein the active region overlaps with the acoustic reflector.

9. The BAW resonator of claim 8, wherein the acoustic reflector comprises one or more material layers or cavities.

10. An integrated circuit IC, comprising: A substrate having a first electrode layer, a second electrode layer and a piezoelectric layer; A first bulk acoustic wave (BAW) resonator includes a first active region and a first frame. The first active region includes a first overlapping area of ​​a first electrode layer, a piezoelectric layer, and a second electrode layer. The first frame is disposed on the piezoelectric layer and surrounds the first active region. The second BAW resonator includes a second active region and a second frame. The second active region includes a first electrode layer, the piezoelectric layer and a second overlapping region of the second electrode layer. The second frame is disposed on the piezoelectric layer and surrounds the second active region. The piezoelectric layer has a first thickness in the first active region and the second active region and a second thickness below the first frame and the second frame, the second thickness being different from the first thickness.

11. The IC of claim 10, wherein a first electrode of the first BAW resonator is electrically coupled to a second electrode of the second BAW resonator, the first electrode being disposed in one of the first electrode layer or the second electrode layer, and the second electrode being disposed in one of the first electrode layer or the second electrode layer.

12. The IC of claim 10, wherein the first frame includes a first wing and the second frame includes a second wing, and wherein the piezoelectric layer has the second thickness below the first wing and the second wing.

13. The IC of claim 12, wherein the first frame and the second frame include a first layer, the first layer being a dielectric or a metal, and wherein the first wing and the second wing include a second dielectric layer or cavity disposed between the piezoelectric layer and the first dielectric layer.

14. The IC of claim 10, wherein the piezoelectric layer includes a portion located between the first BAW resonator and the second BAW resonator, the portion having the second thickness.

15. The IC of claim 14, wherein the portion located between the first BAW resonator and the second BAW resonator is disposed outside the perimeter of the first frame and the second frame.

16. The IC of claim 10, wherein the substrate includes a first acoustic reflector and a second acoustic reflector, and wherein the first active region overlaps with the first acoustic reflector and the second active region overlaps with the second acoustic reflector.

17. An apparatus comprising: First circuit; as well as An electrical filter coupled to the first circuit, the electrical filter including a bulk acoustic wave (BAW) resonator, the BAW resonator comprising: First electrode; Second electrode; A piezoelectric layer is disposed between the first electrode and the second electrode; A substrate on which the first electrode, the second electrode and the piezoelectric layer are disposed, wherein the second electrode is disposed between the substrate and the piezoelectric layer; The active region includes the overlapping region of the first electrode, the piezoelectric layer, and the second electrode; and A frame, which is disposed on the piezoelectric layer and surrounds the active region; The piezoelectric layer has a first thickness in the active region and a second thickness below the frame, the second thickness being different from the first thickness.

18. The device of claim 17, wherein the first circuitry includes a transceiver, and wherein the electrical filter is coupled between the transceiver and the antenna.

19. The device of claim 17, wherein the frame is disposed between a first portion of the piezoelectric layer having the second thickness and the first electrode.

20. The device of claim 19, wherein a second portion of the piezoelectric layer having the second thickness is disposed outside the perimeter of the second electrode on the substrate, and wherein the frame is disposed on the second portion of the piezoelectric layer.

Images