Second overtone acoustic resonator with spurious mode damping

Abstract

Second overtone acoustic resonators with spurious mode dampening are disclosed. In one aspect, an acoustic resonator is formed from two layers of piezoelectric material (416, 418) to form a second overtone acoustic resonator. An additional layer (408), 452, 454) of high-density material is positioned between the two layers, causing a frequency shift that assists in moving spurious modes outside the operational range of the resonator. In exemplary aspects, the high-density material is a metal, although dielectric materials may also be used. By providing this additional layer, the spurious or degenerate modes are mitigated, and frequency trimming is more readily accomplished. This improves the overall efficiency and operation of the acoustic resonator, allowing for a better end-user experience.

Description

Ref. No. P241625-WO-UTL 1SECOND OVERTONE ACOUSTIC RESONATOR WITH SPURIOUS MODE DAMPINGPRIORITY APPEICATION

[0001] The present application is related to U.S. Provisional Patent Application Serial No. 63 / 760,358, filed on February 19, 2025, and entitled “SECOND OVERTONE ACOUSTIC RESONATOR WITH SPURIOUS MODE DAMPING,'’ the contents of which are incorporated herein by reference in their entirety.BACKGROUNDI. Field of the Disclosure

[0002] The technology of the disclosure relates generally to acoustic resonators and more particularly to acoustic resonators that use second overtones, including bulk acoustic wave resonators.II. Background

[0003] Computing devices abound in modern society, and more particularly, mobile communication devices have become increasingly common. The prevalence of these mobile communication devices is driven in part by the many functions that are now enabled on such devices. Increased processing capabilities in such devices means that mobile communication devices have evolved from pure communication tools into sophisticated mobile entertainment centers, thus enabling enhanced user experiences. With the advent of the myriad functions available to such devices, there has been increased pressure to find bandwidth to accommodate the increased data traffic used to support the functions. One solution that has emerged in the newer wireless protocols is the use of higher frequency bands. While some circuitry is amenable to use at the higher frequencies with minimal changes, many filters, including filters based on acoustic resonators, are not so readily converted to the higher frequencies. Finding solutions to assist in converting existing filter technologies for use with the new frequencies provides room for innovation.WT Ref. No. 2867-3528-WORef. No. P241625-WO-UTL 2SUMMARY

[0004] Aspects disclosed in the detailed description include second overtone acoustic resonators with spurious mode dampening. In particular, an acoustic resonator is formed from two layers of piezoelectric material to form a second overtone acoustic resonator. An additional layer of high-density material is positioned between the two layers, causing a frequency shift that assists in moving spurious modes outside the operational range of the resonator. In exemplary aspects, the high-density material is a metal, although dielectric materials may also be used. By providing this additional layer, the spurious or degenerate modes are mitigated, and frequency trimming is more readily accomplished. This improves the overall efficiency and operation of the acoustic resonator, allowing for a better end-user experience.

[0005] In this regard, in one aspect, an acoustic device is disclosed. The acoustic device includes a first electrode, a first side of a first piezoelectric material sub-layer positioned on the first electrode, and a high-density material positioned on a second side of the first piezoelectric material sub-layer. The acoustic device also includes a second piezoelectric material sub-layer positioned on the high-density material, such that the high-density material is sandwiched between the first piezoelectric material sub-layer and the second piezoelectric material sub-layer, and a second electrode positioned on the second piezoelectric material sub-layer.

[0006] In another aspect, a mobile communication device is disclosed. The mobile communication device includes a transceiver comprising an acoustic resonator, the acoustic resonator comprising a first electrode, a first side of a first piezoelectric material sub-layer positioned on the first electrode, and a high-density material positioned on a second side of the first piezoelectric material sub-layer. The acoustic resonator also comprises a second piezoelectric material sub-layer positioned on the high-density material, such that the high-density material is sandwiched between the first piezoelectric material sub-layer and the second piezoelectric material sub-layer, and a second electrode positioned on the second piezoelectric material sub-layer.BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 A is a top plan view of a conventional acoustic resonator;WT Ref. No. 2867-3528-WORef. No. P241625-WO-UTL 3

[0008] Figure IB is a side elevation cross-sectional view of the acoustic resonator of Figure 1A taken along line 1B-1B;

[0009] Figure 1C is a side elevation cross-sectional view of a conventional second overtone acoustic resonator;

[0010] Figure 2A is a graph of impedance against frequency for the resonator of Figure 1C;

[0011] Figure 2B is a graph of Q versus frequency for the resonator of Figure 1C;

[0012] Figure 2C is a graph of Q versus frequency for an ideal resonator in the absence of spurious modes to highlight the deficiencies of the resonator of Figure 1C;

[0013] Figure 3 is a side elevation cross-sectional view of a second overtone resonator with spurious mode damping according to aspects of the present disclosure;

[0014] Figure 4A is a side elevation cross-sectional view of a graduated border ring region of a second overtone resonator with spurious mode damping according to aspects of the present disclosure;

[0015] Figure 4B is a side elevation cross-sectional view of a non-graduated border ring region of a second overtone resonator with spurious mode damping according to aspects of the present disclosure;

[0016] Figure 5A is a graph of impedance against frequency for the resonators of Figures 4A & 4B;

[0017] Figure 5B is a graph of Q versus frequency for the resonators of Figures 4A & 4B;

[0018] Figure 6 is a side elevation cross-sectional view of an alternate border ring region of the second overtone resonator;

[0019] Figure 7 is a side elevation cross-sectional view of an alternate border ring region of the second overtone resonator;

[0020] Figure 8A is a graph of impedance against frequency for the resonator of Figure 7 with different thicknesses for the intermediate material;

[0021] Figure 8B is a graph of Q versus frequency for the resonator of Figure 7 with different thicknesses for the intermediate material;

[0022] Figures 9A-9C illustrate side elevation cross-sectional views of alternate acoustic resonators that may include aspects of the present disclosure; andWT Ref. No. 2867-3528-WORef. No. P241625-WO-UTL 4

[0023] Figure 10 is a block diagram of a wireless transceiver, which may include the second overtone acoustic resonators, according to the present disclosure.DETAILED DESCRIPTION

[0024] The embodiments set forth below represent the necessary information to enable those skilled in the art to practice the embodiments and illustrate the best mode of practicing the embodiments. Upon reading the following description in light of the accompanying drawing figures, those skilled in the art will understand the concepts of the disclosure and will recognize applications of these concepts not particularly addressed herein. It should be understood that these concepts and applications fall within the scope of the disclosure and the accompanying claims.

[0025] It will be understood that although the terms first, second, etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, a first element could be termed a second element, and similarly, a second element could be termed a first element without departing from the scope of the present disclosure. As used herein, the term “and / or” includes any and all combinations of one or more of the associated listed items.

[0026] It will be understood that when an element, such as a layer, region, or substrate, is referred to as being “on” or extending “onto” another element, it can be directly on or extend directly onto the other element, or intervening elements may also be present. In contrast, when an element is referred to as being “directly on” or extending “directly onto” another element, no intervening elements are present. Likewise, it will be understood that when an element, such as a layer, region, or substrate, is referred to as being “over” or extending “over” another element, it can be directly over or extend directly over the other element, or intervening elements may also be present. In contrast, when an element is referred to as being “directly over” or extending “directly over” another element, no intervening elements are present. It will also be understood that when an element is referred to as being “connected” or “coupled” to another element, it can be directly connected or coupled to the other element, or intervening elements may be present. In contrast, when an element is referred to as being “directly connected” or “directly coupled” to another element, no intervening elements are present.WT Ref. No. 2867-3528-WORef. No. P241625-WO-UTL 5

[0027] Relative terms such as “below” or “above” or “upper” or “lower” or “horizontal” or “vertical” may be used herein to describe a relationship of one element, layer, or region to another element, layer, or region as illustrated in the Figures. It will be understood that these terms and those discussed above are intended to encompass different orientations of the device in addition to the orientation depicted in the Figures.

[0028] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. As used herein, the singular forms “a," “an,” and “the” are intended to include the plural forms as well unless the context clearly indicates otherwise. It will be further understood that the terms “comprises," “comprising," “includes,” and / or “including,” when used herein, specify the presence of stated features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0029] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. It will be further understood that terms used herein should be interpreted as having a meaning that is consistent with their meaning in the context of this specification and the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

[0030] In keeping with the above admonition about definitions, the present disclosure uses transceiver in a broad manner. Current industry literature uses “transceiver” in two ways. The first way uses transceiver broadly to refer to a plurality of circuits that send and receive signals. Exemplary circuits may include a baseband processor, an up / down conversion circuit, filters, amplifiers, couplers, and the like coupled to one or more antennas. A second way, used by some authors in the industry literature, refers to a circuit positioned between a baseband processor and a power amplifier circuit as a transceiver. This intermediate circuit may include the up / down conversion circuits, mixers, oscillators, filters, and the like, but generally does not include the power amplifiers. As used herein, the term transceiver is used in the first sense. Where relevant to distinguish between the two definitions, the terms “transceiver chain” and “transceiver circuit” are used respectively.WT Ref. No. 2867-3528-WORef. No. P241625-WO-UTL 6

[0031] Additionally, to the extent that the term “approximately” is used in the claims, it is herein defined to be within five percent (5%).

[0032] Aspects disclosed in the detailed description include second overtone acoustic resonators with spurious mode dampening. In particular, an acoustic resonator is formed from two layers of piezoelectric material to form a second overtone acoustic resonator. An additional layer of high-density material is positioned between the two layers, causing a frequency shift that assists in moving spurious modes outside the operational range of the resonator. In exemplary aspects, the high-density material is a metal, although dielectric materials may also be used. By providing this additional layer, the spurious or degenerate modes are mitigated, and frequency trimming is more readily accomplished. This improves the overall efficiency and operation of the acoustic resonator, allowing for a better end-user experience.

[0033] Before addressing aspects of the present disclosure, a brief overview of conventional acoustic resonators is provided with reference to Figures 1A-2C. A discussion of aspects of the present disclosure begins below with reference to Figure 3.

[0034] Figure 1 A is a top plan view of a conventional acoustic resonator 100, which may be a bulk acoustic wave (BAW) resonator. While shown as a hexagon, it should be appreciated that other polygon shapes, regular and irregular, may also exist. While a top surface 102 is generally planar, optionally, there may be a border region 104 which has thicker electrode material, as better seen in Figure IB. More specifically, the top surface 102 is an upper surface of a first electrode 106. A second electrode 108 is also present and sandwiches a piezoelectric material 110 therebetween. The acoustic resonator 100 may have a homogenous piezoelectric material 110, which may be, for example, scandium aluminum nitride (ScAlN). The electrodes 106, 108 may be made from layers 106A, 108A of tungsten (W) and layers 106B, 108B of aluminum copper (AICu), although other conductive metals may also be used. The border region 104 may be present to confine energy within the resonator, preventing energy from leaking outside it. As illustrated, the layers 106B, 108B are thickened (in the z-axis direction), although other materials may be added between the piezoelectric material 110 and the layers 106A, 108 A (not shown here, but a similar structure is discussed below in reference to Figures 4A & 4B). Although resonator structures are shown with border ring structures on bothWT Ref. No. 2867-3528-WORef. No. P241625-WO-UTL 7top and bottom electrodes, other embodiments may use these border ring structures on only one side.

[0035] The basic BAW acoustic resonator structure is suitable for many applications and uses. However, the current trend for evolving wireless protocols is to increase the frequencies at which wireless transceivers (that may include acoustic resonators) operate. The increase in frequencies causes the size of the acoustic resonators to shrink. In the abstract, such shrinkage is consistent with the general trend to size reduction that dominates the wireless industry. However, as acoustic resonators shrink, their ability to handle power loads diminishes. That is, power density may exceed the operational parameters of the acoustic resonator. One solution to this power density issue is to cascade multiple acoustic devices serially. This solution does resolve the power density issue but imposes an efficiency penalty that arises from the cumulative ohmic resistance (and corresponding loss) of the plural acoustic devices.

[0036] Concerns about such ohmic resistance have caused an investigation into acoustic devices that operate with second or higher overtones achieved through multiple layers of piezoelectric materials. A second overtone acoustic device 150 (which may also be considered an acoustic resonator and may be used inside an acoustic fdter) is illustrated in Figure 1C. In many regards, the acoustic device 150 is identical to the acoustic resonator 100, so similar elements are not renumbered. However, the piezoelectric material 110 is replaced by an acoustic layer 152 having a first sub-layer 154 and a second sub-layer 156. The material of the first sub-layer 154 is denoted “x” and the material of the second sub-layer 156 is denoted “fx”, indicating a flipped material. That is, the polarity of the second sub-layer 156 is flipped relative to the polarity of the first sub-layer 154.

[0037] Preliminary efforts with second overtone acoustic devices, such as the acoustic device 150, indicate performance degradation from spurious or degenerate modes. While impedance may be relatively as expected and desired, Q in particular may vary across frequencies of interest in unacceptable manners. With reference to Figures 2A & 2B, graphs 200A and 200B illustrate performance versus frequency for the acoustic device 150. In particular, graph 200A shows impedance on the y-axis versus frequency on the x-axis. The passband 202 occurs proximate 10 GHz. Graph 200B shows Q versus frequency. While there is a moderately high peak 204 close to 10 GHz, there areWT Ref. No. 2867-3528-WORef. No. P241625-WO-UTL 8numerous lows 206(l)-206(5). This almost sawtooth Q is contrasted with an ideal Q of the resonator where spurious modes are absent, and the only loss mechanism present is material damping represented by Qmat, indicated by line 210, illustrated by graph 200C in Figure 2C. Even at its best, the high peak 204 is still substantially below the ideal Q at the corresponding frequencies.

[0038] Aspects of the present disclosure allow for spurious or degenerative modes to be frequency shifted out of the frequencies of interest, thereby effectively improving the Q over the frequency range of interest. This frequency shift is effectuated by inserting another high-density material (metal or dielectric) between the two sub-layers. Before illustrating, a digression as to the theory behind this approach is provided.

[0039] When displacement fields of different modes supported in a second overtone resonator are considered, particle displacement (i.e., velocity) is maximally different at the mid-plane of the structure, where the particle velocity of the desired longitudinal mode is at a maximum, whereas the velocity of undesired spurious (e.g., shear) modes is zero. By placing a high-density material at this mid-plane, the desired longitudinal mode will experience a significantly large shift in its cutoff frequency compared to the spurious modes, since their particle velocity is zero at that location. The thickness of the piezoelectric layers may then be adjusted to bring back the longitudinal cutoff frequency to the desired range.

[0040] With this understanding, Figure 3 illustrates a side elevation cross-sectional view of an acoustic resonator 300 with spurious mode dampening according to aspects of the present disclosure. With the understanding that the term “top” is relative, but at least with respect to the x-y-z axes provided and to provide a framework for discussion, the acoustic resonator 300 has a top or first electrode 302 formed from two metal layers 304, 306. In an exemplary aspect, the metal layer 304 is AICu, and the metal layer 306 is W. A first piezoelectric material layer 308 is positioned beneath the metal layer 306. An intermediate layer 310 is positioned beneath the first piezoelectric material layer 308 and above a second piezoelectric material layer 312. The first piezoelectric material layer 308 and the second piezoelectric material layer 312 may be ScAlN with reversed polarities as previously discussed. The intermediate layer 310 is a high-density material such as W, platinum (Pt), and molybdenum (Mo), although high-density dielectrics such as hafnium oxide and tantalum oxide are also specifically contemplated. A bottom or secondWT Ref. No. 2867-3528-WORef. No. P241625-WO-UTL 9electrode 314 is positioned beneath the second piezoelectric material layer 312. The second electrode 314 is also formed from two metal layers 316, 318, which may also be AICu and W, respectively.

[0041] Note that the use of the intermediate layer 310 also allows for resonator trimming, a process in which material is removed from a layer to adjust the resonator¬ frequency. Note also that the present discussion also assumes that there is symmetry around the plane formed by the intermediate layer 310. This symmetry allows suppression of unwanted odd resonator spurious modes and maximizes the quality factor and the electromechanical coupling of the desired second overtone mode. Utilizing the intermediate layer 310 for trimming respects this symmetry. It should be appreciated that other layers can be used for trimming, but such an approach may require trimming two layers precisely, potentially complicating manufacturing.

[0042] With the understanding that “high-density” is a relative term, as used herein, this term means at least two times as dense as ScAlN. That is, materials that have a density of 7 g / cm3or greater are considered to be “high-density.” Alternatively, if the piezoelectric material used in layers 308, 312 has a first density, then the second density of the intermediate layer 310 is considered high-density if it is at least two times denser than the first density.

[0043] Within a primary resonator active area, using metal as the intermediate layer 310 allows for no loss of electromechanical coupling associated with any voltage drop across the layer. A dielectric material may have a larger voltage drop; the high dielectric constant (e.g., > 25), combined with the relatively thin vertical (z-axis) dimension, may minimize the drop in electromechanical coupling.

[0044] In contrast, in the border region, there is more flexibility as to material, and there may be reasons to use a dielectric material as the intermediate layer in such border regions. Again, the use of border regions does not reduce the general desire for symmetry. Use of symmetric structures results in better performance because scattering is only possible into modes exhibiting the same symmetry as the piston mode, and no scattering is possible into modes of opposite symmetry. This limit on scattering results in a higher Q. Despite these advantages, the present disclosure also covers situations where there is not such symmetry.WT Ref. No. 2867-3528-WORef. No. P241625-WO-UTL 10

[0045] Figures 4A & 4B illustrate two possible approaches to the border regions. In Figure 4A, a border region 402 is shown in an acoustic device 400. Mass loading is done in the electrodes 404, 406, while the intermediate layer 408 remains at a constant thickness (z-axis). That is as illustrated in the inset 410, wherein a thickness (z-axis) of the layer 412 changes by some value. Further, an additional material 414 is added to both sides of the piezoelectric material layers 416, 418. This additional material 414 incurs a voltage drop, decreasing the excitation of the resonator in the border ring region which helps improve lateral energy confinement.

[0046] In contrast, the acoustic device 450 of Figure 4B uses the intermediate layer 452 to do mass loading. That is, as shown in inset 454, the thickness (z-axis) changes. Flectrodes 456, 458 remain at constant thicknesses (albeit with a bend to accommodate the additional material 414). In exemplary aspects, this additional material may be a dielectric material such as silicon dioxide or silicon nitride, although it should be appreciated that other materials may be used.

[0047] The performance of the devices 400, 450 is compared in graphs 500A, 500B of Figures 5 A & 5B. Specifically, the impedance of both devices 400, 450 is approximately the same as shown in graph 500A, but the Q of the device 450 is generally better than the Q of the device 400, especially at frequencies above 10 GIIz. Neither is yet close to the ideal Q of graph 200C, but both are better than the Q of the device 150.

[0048] While the devices 400, 450 contemplate a lateral dimension (x-axis) of the intermediate layer that ends with the end of the electrodes (see generally lines 460A, 460B in Figures 4A & 4B respectively), the present disclosure is not so limited. Figure 6 illustrates a device 600 where the intermediate layer 602 extends to a lateral edge 604 of the device 600. Figure 7 illustrates a device 700 where the intermediate layer 702 extends past a lateral edge of the electrodes 704, 706 by a distance (e.g., wMxO), but not to the lateral edge 708 of the device 700.

[0049] Figures 8A and 8B illustrate performances of the device 700 with different dimensions for wMxO. In particular, graph 800 of Figure 8A shows that the impedance of the device remains essentially the same regardless of wMxO, but graph 850 of Figure 8B shows that Q may vary by frequency and by the wMxO. Accordingly, the selection of this dimension allows designers more options. Also note that the quality factor of theWT Ref. No. 2867-3528-WORef. No. P241625-WO-UTL 11device 700 in Fig.7, shown in Fig. 8B, is generally better than the quality factor of devices 400 and 450 shown in Fig. 5B.

[0050] While the above discussion has described using thin film bulk acoustic wave (FB AR) technology, the present disclosure is not so limited. The teachings of the present disclosure may be extended to other BAW technologies, including solidly mounted resonators (SMR), in which the resonators are mounted on silicon substrates, as illustrated in Figure 9A. That is, acoustic device 900 has a silicon substrate 902 on which a bottom reflector 904 is positioned. The bottom reflector 904 may, for example, be alternating layers of silicon dioxide 906 and tungsten 908. A bottom electrode consisting of layers 910 and 912 may be positioned on the bottom reflector 904. A first piezoelectric material layer 916A is positioned on the bottom electrode layer 912. A high-density layer 917 is positioned on top of the first piezoelectric layer 916A and is formed from a high-density material. A second piezoelectric layer 916B with inverted polarity with respect to 916A is positioned on top of the high-density layer 917. A top electrode consisting of layers 918 and 920 is positioned between the second piezoelectric layer 916B and a top reflector 922 formed from alternating layers of silicon dioxide 924 and tungsten 926.

[0051] Figure 9B is similar to device 940. Note that the first piezoelectric layer is labeled 914 in Figure 9B (instead of 916A). An additional connection 942 exists between conductive reflective layers 944. This approach may reduce ohmic loss in the resonator. Conductive reflective layers 944 may be aluminum, copper, or other conductive material.

[0052] Figure 9C is similar to device 950, but low impedance areas 952, 954 directly opposing the top and bottom electrodes 910, 920 are air cavities (e.g., the silicon dioxide is removed).

[0053] The acoustic resonator with spurious mode dampening according to aspects disclosed herein may be provided in or integrated into any processor-based device. Examples, without limitation, include a set-top box, an entertainment unit, a navigation device, a communications device, a fixed location data unit, a mobile location data unit, a global positioning system (GPS) device, a mobile phone, a cellular phone, a smartphone, a session initiation protocol (SIP) phone, a tablet, a phablet, a server, a computer, a portable computer, a mobile computing device, a wearable computing device (e.g., a smartwatch, a health or fitness tracker, eyewear, etc.), a desktop computer, a personal digital assistant (PDA), a monitor, a computer monitor, a television, a tuner, a radio, aWT Ref. No. 2867-3528-WORef. No. P241625-WO-UTL 12satellite radio, a music player, a digital music player, a portable music player, a digital video player, a video player, a digital video disc (DVD) player, a portable digital video player, an automobile, a vehicle component, avionics systems, a drone, and a multicopter.

[0054] Figure 10 is a schematic diagram of an exemplary communication device 1000 wherein the acoustic resonators of the present disclosure can be provided. Herein, the communication device 1000 can be any type of communication device, such as those listed above as well as access points, base stations (e.g., eNB or gNB), and any other type of wireless communication devices that support wireless communications, such as cellular, wireless local area network (WLAN), Bluetooth, Ultra-wideband (UWB), and near field communications.

[0055] More particularly, the communication device 1000 will generally include a control system 1002, a baseband processor 1004, transmit circuitry 1006, receive circuitry 1008, antenna switching circuitry 1010, multiple antennas 1012, and user interface circuitry 1014. In a non-limiting example, the control system 1002 can be a field-programmable gate array (FPGA) or an application-specific integrated circuit (ASIC), as an example. In this regard, the control system 1002 can include at least a microprocessor(s), an embedded memory circuit(s), and a communication bus interface(s). The receive circuitry 1008 receives radio frequency signals via the antennas 1012 and through the antenna switching circuitry 1010 from one or more base stations. A low noise amplifier and a filter (e.g., an acoustic filter based on an acoustic resonator of the present disclosure) of the receive circuitry 1008 cooperate to amplify and remove broadband interference from the received signal for processing. Downconversion and digitization circuitry (not shown) will then downconvert the filtered, received signal to an intermediate or baseband frequency signal, which is then digitized into one or more digital streams using an analog-to-digital converter(s) (ADC).

[0056] The baseband processor 1004 processes the digitized received signal to extract the information or data bits conveyed in the received signal. This processing typically comprises demodulation, decoding, and error correction operations. The baseband processor 1004 is generally implemented in one or more digital signal processors (DSPs) and ASICs.

[0057] For transmission, the baseband processor 1004 receives digitized data, which may represent voice, data, or control information, from the control system 1002, which itWT Ref. No. 2867-3528-WORef. No. P241625-WO-UTL 13encodes for transmission. The encoded data is output to the transmit circuitry 1006, where a digital-to-analog converter(s) (DAC) converts the digitally encoded data into an analog signal, and a modulator modulates the analog signal onto a carrier signal that is at a desired transmit frequency or frequencies. A power amplifier will amplify the modulated earner signal to a level appropriate for transmission and deliver the modulated carrier signal to the antennas 1012 through the antenna switching circuitry 1010. Acoustic resonators of the present disclosure may be present at various places in the transmit circuitry 1006 (e.g., within an acoustic filter). The multiple antennas 1012 and the replicated transmit and receive circuitries 1006, 1008 may provide spatial diversity. Modulation and processing details will be understood by those skilled in the art.

[0058] It is also noted that the operational steps described in any of the exemplary aspects herein are described to provide examples and discussion. The operations described may be performed in numerous different sequences other than the illustrated sequences. Furthermore, operations described in a single operational step may actually be performed in a number of different steps. Additionally, one or more operational steps discussed in the exemplary aspects may be combined. It is to be understood that the operational steps illustrated in the flowchart diagrams may be subject to numerous different modifications, as will be readily apparent to one of skill in the art. Those of skill in the art will also understand that information and signals may be represented using any of a variety of different technologies and techniques. For example, data, instructions, commands, information, signals, bits, symbols, and chips that may be referenced throughout the above description may be represented by voltages, currents, electromagnetic waves, magnetic fields or particles, optical fields or particles, or any combination thereof.

[0059] The previous description of the disclosure is provided to enable any person skilled in the art to make or use the disclosure. Various modifications to the disclosure will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other variations. Thus, the disclosure is not intended to be limited to the examples and designs described herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.WT Ref. No. 2867-3528-WO

Claims

Ref. No. P241625-WO-UTL 14What is claimed is:

1. An acoustic device comprising:a first electrode;a first side of a first piezoelectric material sub-layer positioned on the first electrode;a high-density material positioned on a second side of the first piezoelectric material sub-layer;a second piezoelectric material sub-layer positioned on the high-density material, such that the high-density material is sandwiched between the first piezoelectric material sub-layer and the second piezoelectric material sub-layer; anda second electrode positioned on the second piezoelectric material sub-layer.

2. The acoustic device of claim 1, wherein the acoustic device comprises an acoustic resonator.

3. The acoustic device of claim 1, wherein the acoustic device is a bulk acoustic wave (BAW) device.

4. The acoustic device of claim 1 , wherein the high-density material is a metal.

5. The acoustic device of claim 4, wherein the metal is selected from the group consisting of tungsten, platinum, and molybdenum.

6. The acoustic device of claim 1, wherein the high-density material is a dielectric material.

7. The acoustic device of claim 6, wherein the high-density material is selected from the group consisting of hafnium oxide and tantalum oxide.

8. The acoustic device of claim 1, further comprising a border region formed at a lateral edge of the acoustic device.WT Ref. No. 2867-3528-WORef. No. P241625-WO-UTL 159. The acoustic device of claim 8, wherein the high-density material extends into the border region.

10. The acoustic device of claim 8, wherein the high-density material extends to the lateral edge of the acoustic device.

11. The acoustic device of claim 8, wherein the border region includes a mass loading region.

12. The acoustic device of claim 11 , wherein the high-density material provides the mass loading region.

13. The acoustic device of claim 11, wherein the first electrode and the second electrode provide the mass loading region.

14. The acoustic device of claim 1, wherein the acoustic device is formed with thin film bulk acoustic wave technology.

15. The acoustic device of claim 1, further comprising a silicon substrate over which a second side of the first electrode is positioned.

16. The acoustic device of claim 15 , further comprising a reflector positioned between the silicon substrate and the second side of the first electrode.

17. The acoustic device of claim 16, wherein the reflector comprises a plurality of heterogeneous material layers and wherein at least one of the heterogeneous material layers is electrically coupled to the first electrode.

18. The acoustic device of claim 1 incorporated into a transceiver.

19. The acoustic device of claim 1 integrated into a device selected from the group consisting of: a set-top box; an entertainment unit; a navigation device; a communicationsWT Ref. No. 2867-3528-WORef. No. P241625-WO-UTL 16device; a fixed location data unit; a mobile location data unit; a global positioning system (GPS) device; a mobile phone; a cellular phone; a smartphone; a session initiation protocol (SIP) phone; a tablet; a phablet; a server; a computer; a portable computer; a mobile computing device; a wearable computing device; a desktop computer; a personal digital assistant (PDA); a monitor; a computer monitor; a television; a tuner; a radio; a satellite radio; a music player; a digital music player; a portable music player; a digital video player; a video player; a digital video disc (DVD) player; a portable digital video player; an automobile; a vehicle component; avionics systems; a drone; and a multicopter.

20. A mobile communication device comprising:a transceiver comprising an acoustic resonator, the acoustic resonator comprising:a first electrode;a first side of a first piezoelectric material sub-layer positioned on the first electrode;a high-density material positioned on a second side of the first piezoelectric material sub-layer;a second piezoelectric material sub-layer positioned on the high-density material, such that the high-density material is sandwiched between the first piezoelectric material sub-layer and the second piezoelectric material sub-layer; anda second electrode positioned on the second piezoelectric material sublayer.WT Ref. No. 2867-3528-WO

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