Bulk acoustic resonator, bulk acoustic wave filter, and electronic device

Abstract

The present invention relates to the technical field of communications, and provides a bulk acoustic resonator, a bulk acoustic wave filter, and an electronic device. The bulk acoustic resonator of the present invention comprises: a substrate, and a first electrode, a piezoelectric layer and a second electrode which are sequentially arranged on the substrate; the bulk acoustic resonator is divided into a working area, a transition area surrounding the working area, and a peripheral area surrounding the transition area; the bulk acoustic resonator comprises a first air gap and a second air gap which are located in the transition area; in a direction perpendicular to the substrate, the first air gap at least extends through part of the thickness of the piezoelectric layer; the second electrode comprises a first main body portion located in the working area, and an edge portion located in the transition area and connected to the first main body portion; the first main body portion is in contact with the piezoelectric layer; there is a certain gap between the edge portion and the piezoelectric layer, so as to form the second air gap; and the orthographic projection of the second air gap on a layer where the substrate is located covers the orthographic projection of the first air gap on the layer where the substrate is located.

Description

Bulk acoustic wave resonator, bulk acoustic wave filter and electronic device TECHNICAL FIELD

[0001] The present disclosure belongs to the technical field of communication, and particularly relates to a bulk acoustic wave resonator, a bulk acoustic wave filter and an electronic device. BACKGROUND

[0002] In the field of mobile communication, because the total available frequency range allocated is narrow, and there are many frequency bands for mobile communication, the spacing between adjacent frequency bands is very narrow (about several megahertz to tens of megahertz), and the bandwidth of a single frequency band is very narrow (tens of megahertz), so it is required that the filter used in a mobile phone must have the performance characteristics of small in-band ripple, large out-of-band suppression and good rectangularity. The conventional microstrip filter is large in size, has insufficient out-of-band suppression and poor rectangularity, and cannot be corresponded; the cavity filter is very large in size and cannot be corresponded; the dielectric filter has large in-band insertion loss and poor rectangularity, and cannot be corresponded; and the IPD filter has large in-band ripple and poor rectangularity, and cannot be corresponded.

[0003] As a basic structural unit of a bulk acoustic wave filter, the existing bulk acoustic wave resonator uses a silicon wafer as a substrate material, and a sandwich structure is used thereon, from bottom to top, a first electrode, a piezoelectric material and a second electrode. The working principle is that a radio frequency signal is transmitted from the electrode at one end of the resonator, and then converted into a mechanical vibration acoustic signal through inverse piezoelectric effect at the interface between the piezoelectric material and the metal electrode. The acoustic signal forms a standing wave with a certain frequency in the sandwich structure of the first electrode, the piezoelectric material and the second electrode, and the frequency of the radio frequency signal is equal to the resonant frequency of the resonator. The acoustic signal is transmitted to the electrode at the other end of the resonator, and the acoustic signal is converted into a radio frequency signal through piezoelectric effect at the interface between the metal electrode and the piezoelectric material. The resonator has a fixed resonant frequency, and when the frequency of the radio frequency signal is equal to the resonant frequency of the resonator, the conversion efficiency of the radio frequency signal to the acoustic signal to the radio frequency signal is high; when the frequency of the radio frequency signal is not equal to the resonant frequency of the resonator, the conversion efficiency of the radio frequency signal to the acoustic signal to the radio frequency signal is very low, and most of the radio frequency signal cannot be transmitted from the resonator, that is, the resonator functions as a filter to filter the radio frequency signal.

[0004] SUMMARY

[0005] The present application aims to at least solve one of the technical problems existing in the prior art, and provides a bulk acoustic wave resonator, a bulk acoustic wave filter and an electronic device.

[0006] The present disclosure provides a bulk acoustic wave resonator, which comprises: a substrate substrate, a first electrode, a piezoelectric layer and a second electrode are sequentially arranged on the substrate substrate; the projections of any two of the first electrode, the piezoelectric layer and the second electrode on the layer where the substrate substrate is located at least partially overlap; wherein,

[0007] The bulk acoustic resonator is divided into an operating region, a transition region surrounding the operating region, and a peripheral region surrounding the transition region; the bulk acoustic resonator includes a first air gap and a second air gap in the transition region;

[0008] In a direction perpendicular to the substrate, the first air gap at least penetrates a partial thickness of the piezoelectric layer; the second electrode includes a first main portion in the operating region, and an edge portion in the transition region and connected to the first main portion, the first main portion being in contact with the piezoelectric layer, and the edge portion having a gap with the piezoelectric layer to form the second air gap;

[0009] The second air gap in the orthographic projection of the layer where the substrate is located covers the orthographic projection of the first air gap in the layer where the substrate is located.

[0010] The substrate has a first groove portion; the substrate includes a first surface and a second surface oppositely arranged along the thickness direction thereof; the opening of the first groove portion is located at the first surface, and the orthographic projection of the opening of the first groove portion in the plane where the second surface is located is located within the orthographic projection of the first electrode in the plane where the second surface is located.

[0011] The first air gap penetrates the piezoelectric layer and a partial thickness of the first electrode and the substrate; the depth of the first air gap penetrating the substrate is less than the depth of the first groove portion.

[0012] The bulk acoustic resonator further includes a support layer arranged between the first electrode and the first surface; the orthographic projection of the support layer in the plane where the second surface is located covers the orthographic projection of the opening of the first groove portion in the plane where the second surface is located.

[0013] The orthographic projection of the first air gap in the plane where the second surface is located has a certain spacing with the orthographic projection of the first groove portion in the plane where the second surface is located.

[0014] The bulk acoustic resonator further includes at least one release hole penetrating the piezoelectric layer and the first electrode along the thickness direction of the substrate; the release hole is located in the peripheral region.

[0015] The first groove portion includes a first sub-groove portion in the operating region and the transition region, and at least one second sub-groove portion in the peripheral region; the first sub-groove portion is in communication with the second sub-groove portion, and the orthographic projection of one of the second sub-groove portions and one of the release holes in the plane where the second surface is located at least partially overlaps.

[0016] The first electrode comprises a second main part located in the working area and the transition area, and at least one first auxiliary part located in the peripheral area; the first auxiliary part is connected with the second main part, and the projection of any two of the first auxiliary part, the second sub-groove part and the release hole on the plane where the second surface is located at least partially overlaps.

[0017] The first air gap is multiple, and the multiple first air gaps are arranged around the transition area.

[0018] The overlapping area of the projection of the first electrode, the piezoelectric layer and the second electrode on the substrate is circular.

[0019] The bulk acoustic wave resonator further comprises a mass loading layer arranged on the side of the second electrode away from the substrate.

[0020] The bulk acoustic wave filter comprises a plurality of electrically connected bulk acoustic wave resonators; the bulk acoustic wave resonator is any one of the bulk acoustic wave resonators described above.

[0021] The bulk acoustic wave filter comprises an input terminal and an output terminal, and a series branch and at least one parallel branch connected between the input terminal and the output terminal; the plurality of bulk acoustic wave resonators comprises a plurality of first bulk acoustic wave resonators and at least one second bulk acoustic wave resonator.

[0022] The series branch comprises a plurality of the first bulk acoustic wave resonators connected in series between the input terminal and the output terminal; the parallel branch comprises the second bulk acoustic wave resonator; one end of the second bulk acoustic wave resonator is connected with the first bulk acoustic wave resonator, and the other end is connected with a reference voltage terminal.

[0023] The number of the first bulk acoustic wave resonators is 5, and the number of the second bulk acoustic wave resonators is 5.

[0024] a first electrode of a first one of the first bulk acoustic resonators is connected to an input terminal, a second electrode of the first one of the first bulk acoustic resonators is connected to a second electrode of a first one of the second bulk acoustic resonators and a second electrode of a second one of the first bulk acoustic resonators; a first electrode of the second one of the first bulk acoustic resonators is connected to a first electrode of a second one of the second bulk acoustic resonators and a first electrode of a third one of the first bulk acoustic resonators; a second electrode of the third one of the first bulk acoustic resonators is connected to a second electrode of a third one of the second bulk acoustic resonators and a first electrode of a fourth one of the first bulk acoustic resonators; a first electrode of the fourth one of the first bulk acoustic resonators is connected to a first electrode of a fourth one of the second bulk acoustic resonators and a first electrode of a fifth one of the first bulk acoustic resonators; and a second electrode of the fifth one of the first bulk acoustic resonators is connected to an output terminal and a second electrode of a fifth one of the second bulk acoustic resonators.

[0025] a first electrode of a first one of the second bulk acoustic resonators, a second electrode of a second one of the second bulk acoustic resonators, a first electrode of a third one of the second bulk acoustic resonators, a second electrode of a fourth one of the second bulk acoustic resonators, and a first electrode of a fifth one of the second bulk acoustic resonators are connected to a reference electrode.

[0026] wherein the bulk acoustic wave filter comprises, in sequence in a direction away from the substrate, a first conductive layer, a semiconductor layer, and a second conductive layer;

[0027] the first electrodes of the first bulk acoustic resonators and the first electrodes of the second bulk acoustic resonators are located in the first conductive layer;

[0028] the piezoelectric layers of the first bulk acoustic resonators and the piezoelectric layers of the second bulk acoustic resonators are located in the semiconductor layer;

[0029] the second electrodes of the first bulk acoustic resonators and the second electrodes of the second bulk acoustic resonators are located in the second conductive layer.

[0030] The first electrode of the second first bulk acoustic resonator and the first electrode of the second second bulk acoustic resonator are connected through a first connecting electrode; the first electrode of the second first bulk acoustic resonator and the first electrode of the third first bulk acoustic resonator are connected through a second connecting electrode; the first electrode of the fourth first bulk acoustic resonator and the first electrode of the fourth second bulk acoustic resonator are connected through a third connecting electrode; the first electrode of the fourth first bulk acoustic resonator and the first electrode of the fifth first bulk acoustic resonator are connected through a fourth connecting electrode; the first electrode of the first first bulk acoustic resonator is connected with the input terminal through a fifth connecting electrode; the first electrode of the first second bulk acoustic resonator is connected with the reference electrode through a sixth connecting electrode; the first electrode of the third second bulk acoustic resonator is connected with the reference electrode through a seventh connecting electrode; and the first electrode of the fifth second bulk acoustic resonator is connected with the reference electrode through an eighth connecting electrode.

[0031] The first connecting electrode, the second connecting electrode, the third connecting electrode, the fourth connecting electrode, the fifth connecting electrode, the sixth connecting electrode, the seventh connecting electrode, and the eighth connecting electrode are all located on the first conductive layer.

[0032] At least one of the first connecting electrode, the second connecting electrode, the third connecting electrode, the fourth connecting electrode, the fifth connecting electrode, the sixth connecting electrode, the seventh connecting electrode, and the eighth connecting electrode monotonically increases or monotonically decreases in line width along the respective extension direction.

[0033] The second electrode of the first first bulk acoustic resonator and the second electrode of the second first bulk acoustic resonator are connected through a ninth connecting electrode; the second electrode of the first first bulk acoustic resonator and the second electrode of the first second bulk acoustic resonator are connected through a tenth connecting electrode; the second electrode of the third first bulk acoustic resonator and the second electrode of the fourth first bulk acoustic resonator are connected through an eleventh connecting electrode; the second electrode of the third first bulk acoustic resonator and the second electrode of the third second bulk acoustic resonator are connected through a twelfth connecting electrode; the second electrode of the fifth first bulk acoustic resonator and the second electrode of the fifth second bulk acoustic resonator are connected through a thirteenth connecting electrode; the second electrode of the second second bulk acoustic resonator and the reference electrode are connected through a fourteenth connecting electrode; the second electrode of the fourth second bulk acoustic resonator and the reference electrode are connected through a fifteenth connecting electrode; and the second electrode of the fifth second bulk acoustic resonator and the reference electrode are connected through a sixteenth connecting electrode.

[0034] The ninth connection electrode, the tenth connection electrode, the eleventh connection electrode, the twelfth connection electrode, the thirteenth connection electrode, the fourteenth connection electrode, the fifteenth connection electrode, and the sixteenth connection electrode are located on the second conductive layer.

[0035] At least one of the ninth connection electrode, the tenth connection electrode, the eleventh connection electrode, the twelfth connection electrode, the thirteenth connection electrode, the fourteenth connection electrode, the fifteenth connection electrode, and the sixteenth connection electrode has a line width along a respective extension direction that monotonically increases or monotonically decreases.

[0036] The first conductive layer further includes a first connection pad, a second connection pad, a third connection pad, a fourth connection pad, a fifth connection pad, a sixth connection pad, and a seventh connection pad.

[0037] The second conductive layer further includes an eighth connection pad, a ninth connection pad, a tenth connection pad, an eleventh connection pad, a twelfth connection pad, a thirteenth connection pad, and a fourteenth connection pad.

[0038] The first connection pad is connected to the fifth connection electrode and is connected to the eighth connection pad through a first connection via hole that penetrates the semiconductor layer.

[0039] The second connection pad is connected to the ninth connection pad through a second connection via hole that penetrates the semiconductor layer, and the ninth connection pad is connected to the fourteenth connection electrode.

[0040] The third connection pad is connected to the tenth connection pad through a third connection via hole that penetrates the semiconductor layer, and the tenth connection pad is connected to the fifteenth connection electrode.

[0041] The fourth connection pad is connected to the eleventh connection pad through a fourth connection via hole that penetrates the semiconductor layer, and the eleventh connection pad is connected to the sixteenth connection electrode.

[0042] The fifth connection pad is connected to the sixth connection electrode and is connected to the twelfth connection pad through a fifth connection via hole that penetrates the semiconductor layer.

[0043] The sixth connection pad is connected to the seventh connection electrode and is connected to the thirteenth connection pad through a sixth connection via hole that penetrates the semiconductor layer.

[0044] The seventh connection pad is connected to the eighth connection electrode and is connected to the fourteenth connection pad through a seventh connection via hole that penetrates the semiconductor layer.

[0045] The first connection via is in the second surface plane, and the first connection via is in the second surface plane.

[0046] The second connection via is in the second surface plane, and the second connection via is in the second surface plane.

[0047] The third connection via is in the second surface plane, and the third connection via is in the second surface plane.

[0048] The fourth connection via is in the second surface plane, and the fourth connection via is in the second surface plane.

[0049] The fifth connection via is in the second surface plane, and the fifth connection via is in the second surface plane.

[0050] The sixth connection via is in the second surface plane, and the sixth connection via is in the second surface plane.

[0051] The seventh connection via is in the second surface plane, and the seventh connection via is in the second surface plane.

[0052] The semiconductor layer further comprises a first through hole, a second through hole, a third through hole and a fourth through hole along the thickness direction thereof;

[0053] The first through hole is in the second surface plane, and the first through hole is in the second surface plane.

[0054] The second through hole is in the second surface plane, and the second through hole is in the second surface plane.

[0055] The third through hole is in the second surface plane, and the third through hole is in the second surface plane.

[0056] The fourth through hole is in the second surface plane, and the fourth through hole is in the second surface plane.

[0057] Five first bulk acoustic wave filters and five second bulk acoustic wave filters are arranged in three rows.

[0058] the second second bulk acoustic resonator, the fourth second bulk acoustic resonator, and the fifth first bulk acoustic resonator are located in the first row;

[0059] the first first bulk acoustic resonator, the second first bulk acoustic resonator, the fourth first bulk acoustic resonator, and the fifth second bulk acoustic resonator are located in the second row;

[0060] the first second bulk acoustic resonator, the third first bulk acoustic resonator, and the third second bulk acoustic resonator are located in the third row.

[0061] wherein an average area of each of the first bulk acoustic resonators is less than an average area of each of the second bulk acoustic resonators.

[0062] An electronic device is provided, which includes the bulk acoustic wave filter of any one of the above. BRIEF DESCRIPTION OF DRAWINGS

[0063] FIG. 1 is a schematic diagram of a structure of a back-etch bulk acoustic resonator.

[0064] FIG. 2 is a schematic diagram of a structure of a thin-film bulk acoustic resonator.

[0065] FIG. 3 is a schematic diagram of a structure of another thin-film bulk acoustic resonator.

[0066] FIG. 4 is a schematic diagram of a structure of a solidly mounted bulk acoustic resonator.

[0067] FIG. 5a is a schematic diagram of an exemplary bulk acoustic resonator according to an embodiment of the present disclosure.

[0068] FIG. 5b is a schematic diagram of another exemplary bulk acoustic resonator according to an embodiment of the present disclosure.

[0069] FIG. 6 is a top view of a first slot portion of a bulk acoustic resonator according to an embodiment of the present disclosure.

[0070] FIG. 7 is a top view of a first electrode of a bulk acoustic resonator according to an embodiment of the present disclosure.

[0071] FIG. 8 is a schematic diagram of an intermediate product formed in step S11 of a method of manufacturing a bulk acoustic resonator according to an embodiment of the present disclosure.

[0072] FIG. 9 is a schematic diagram of an intermediate product formed in step S12 of a method of manufacturing a bulk acoustic resonator according to an embodiment of the present disclosure.

[0073] FIG. 10 is a schematic diagram of an intermediate product formed in step S13 of a method of manufacturing a bulk acoustic resonator according to an embodiment of the present disclosure.

[0074] Fig. 11 is a schematic view of an intermediate product formed in step S14 of the method for manufacturing a bulk acoustic wave resonator according to an embodiment of the present disclosure.

[0075] Fig. 12 is a schematic view of an intermediate product formed in step S15 of the method for manufacturing a bulk acoustic wave resonator according to an embodiment of the present disclosure.

[0076] Fig. 13 is a schematic view of an intermediate product formed in step S16 of the method for manufacturing a bulk acoustic wave resonator according to an embodiment of the present disclosure.

[0077] Fig. 14 is a schematic view of an intermediate product formed in step S17 of the method for manufacturing a bulk acoustic wave resonator according to an embodiment of the present disclosure.

[0078] Fig. 15 is a schematic view of an intermediate product formed in step S18 of the method for manufacturing a bulk acoustic wave resonator according to an embodiment of the present disclosure.

[0079] Fig. 16 is a schematic view of an intermediate product formed in step S19 of the method for manufacturing a bulk acoustic wave resonator according to an embodiment of the present disclosure.

[0080] Fig. 17 is a schematic view of an intermediate product formed in step S110 of the method for manufacturing a bulk acoustic wave resonator according to an embodiment of the present disclosure.

[0081] Fig. 18 is a schematic view of an intermediate product formed in step S111 of the method for manufacturing a bulk acoustic wave resonator according to an embodiment of the present disclosure.

[0082] Fig. 19 is a circuit diagram of an exemplary bulk acoustic wave filter according to an embodiment of the present disclosure.

[0083] Fig. 20 is a top view of a substrate of a bulk acoustic wave filter according to an embodiment of the present disclosure.

[0084] Fig. 21 is a top view of a first conductive layer of a bulk acoustic wave filter according to an embodiment of the present disclosure.

[0085] Fig. 22 is a top view of a semiconductor layer of a bulk acoustic wave filter according to an embodiment of the present disclosure.

[0086] Fig. 23 is a top view of a second conductive layer of a bulk acoustic wave filter according to an embodiment of the present disclosure.

[0087] Fig. 24 is a top view of a second air gap of a bulk acoustic wave filter according to an embodiment of the present disclosure.

[0088] Fig. 25 is a top view of a first air gap of a bulk acoustic wave filter according to an embodiment of the present disclosure. DETAILED DESCRIPTION

[0089] In order for those skilled in the art to better understand the technical solutions of the present application, the present application will be described in further detail below with reference to the drawings and specific embodiments.

[0090] Unless otherwise defined, technical terms or scientific terms used in the present disclosure shall have the ordinary meaning as understood by a person of ordinary skill in the art to which the present disclosure pertains. The terms "first", "second", and similar terms used in the present disclosure do not denote any order, quantity, or importance, but are used to distinguish different components. Similarly, the terms "one", "a", or "the" do not denote a quantity restriction, but mean that at least one exists. The terms "include", "comprise", and similar terms mean that the elements or objects before the terms encompass the elements or objects listed after the terms and their equivalents, and do not exclude other elements or objects. The terms "connect" or "connected" and similar terms are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. The terms "upper", "lower", "left", "right", and the like are used only to represent relative positional relationships, and when the absolute positions of the described objects are changed, the relative positional relationships can also be changed accordingly.

[0091] As shown in FIGS. 1-4, in order to reduce the insertion loss in the filtering process, the acoustic wave signal needs to be limited as much as possible in the piezoelectric layer 12 between the first electrode and the second electrode 13 to prevent the acoustic wave signal from spreading outward, and therefore an acoustic wave reflector is usually constructed on the upper and lower surfaces of the resonator. The upper surface generally uses air medium with low acoustic impedance as the reflector, and according to the construction of the acoustic wave reflector on the lower surface, the bulk acoustic resonator is divided into three categories: a back-etch bulk acoustic resonator, as shown in FIG. 1; a film bulk acoustic resonator (abbreviated as FBAR), as shown in FIGS. 2 and 3; and a solid mounted resonator (abbreviated as SMR), as shown in FIG. 4. Among them, the FBAR is constructed with a first groove part 102 etched on the substrate as an acoustic reflector under the first electrode, and then the first electrode is supported by the support layer 14, as shown in FIG. 2. Alternatively, the first groove part 102 is formed by the support layer 14 as an acoustic reflector, as shown in FIG. 3; the SMR is constructed with an acoustic mirror structure 15 formed by alternately and repeatedly stacking high acoustic impedance layers 151 and low acoustic impedance material layers 152 under the first electrode; and the back-etch bulk acoustic resonator is constructed with a first cavity 101 formed on the substrate as an air layer under the first electrode by deep etching on the back of the silicon substrate.

[0092] In existing bulk acoustic resonator products, in order to reduce the insertion loss in the filtering process, the acoustic wave signal needs to be limited as much as possible inside the piezoelectric material (i.e., the piezoelectric layer) to prevent the acoustic wave signal from spreading outward, and therefore an acoustic wave reflector is usually constructed on the upper and lower surfaces of the resonator. In the embodiments of the present disclosure, in order to reduce the lateral acoustic wave loss, the following technical solutions are provided.

[0093] Figure 5a is a schematic diagram of an example bulk acoustic resonator according to embodiments of the present disclosure. As shown in Figure 5a, the bulk acoustic resonator according to embodiments of the present disclosure is divided into an operation region Q1 and a peripheral region Q2 surrounding the operation region Q1, and a transition region between the operation region and the peripheral region. The bulk acoustic resonator includes a substrate 10, and a first electrode 11, a piezoelectric layer 12, and a second electrode 13 disposed in sequence on the substrate 10. A space between the support layer 14 and the substrate 10 defines a first slot portion 102 (acoustic reflection layer). The orthographic projection of any two of the first electrode 11, the piezoelectric layer 12, and the second electrode 13 on the substrate 10 at least partially overlaps. The substrate 10 includes a first surface and a second surface disposed opposite along the thickness direction thereof; the opening of the first slot portion 102 is located at the first surface, and the orthographic projection of the opening of the first slot portion 102 on the plane of the second surface is located within the orthographic projection of the first electrode 11 on the plane of the second surface.

[0094] Specifically, in the operation region Q1, the first electrode 11 and the second electrode 13 are respectively attached to the upper and lower surfaces of the piezoelectric layer 12, and in the transition region, at least one first air gap 41 is provided which penetrates at least part of the thickness of the piezoelectric layer 12 in a direction perpendicular to the substrate 10. The second electrode 13 includes a first main portion located in the operation region Q1 and an edge portion located in the transition region and connected to the first main portion; the first main portion is in contact with the piezoelectric layer 12, and the edge portion has a gap with the piezoelectric layer 12 to form a second air gap 42. Moreover, the orthographic projection of the second air gap 42 on the substrate 10 covers the orthographic projection of the first air gap 41 on the substrate 10. In some examples, the first air gap 41 can completely penetrate the piezoelectric layer 12, or can only penetrate part of the thickness of the piezoelectric layer 12. In some examples, the first air gap 41 can penetrate not only the piezoelectric layer 12 but also the first electrode 11. In embodiments of the present disclosure, only the case where the first air gap 41 penetrates the piezoelectric layer 12 is taken as an example.

[0095] The input radio frequency signal is converted into acoustic wave signal in the piezoelectric layer 12 by inverse piezoelectric effect at the interface between the second electrode 13 and the piezoelectric layer 12, and the acoustic wave signal is propagated longitudinally in the piezoelectric layer 12, and is converted into radio frequency signal again by piezoelectric effect at the interface between the first electrode 11 and the piezoelectric layer 12 and is transmitted out. The air gap below the resonator and the air layer above the resonator act as acoustic reflector, which limits the acoustic signal in the resonator structure instead of dissipating, and reduces the loss of the resonator. At the same time, the piezoelectric layer 12 is broken at the transition zone to form the first air gap 41, i.e. to form a longitudinal air wall structure, so that the acoustic wave propagating transversely near the piezoelectric layer 12 and the first electrode 11 is totally reflected at the air wall structure and returns to the piezoelectric resonator instead of propagating outward and dissipating, thereby reducing the loss of the device. At the same time, the first main part of the second electrode 13 is located in the working zone Q1, and the edge part is located in the transition zone. The first main part is in contact with the piezoelectric layer 12, and the edge part has a certain gap with the piezoelectric layer 12 to form the second air gap 42. Through the second air gap 42, the acoustic wave propagating transversely in the piezoelectric layer 12 can be totally reflected at the wall structure and return to the piezoelectric resonator instead of propagating outward and dissipating, thereby further reducing the loss of the device.

[0096] In some examples, FIG. 5b is a schematic diagram of another exemplary bulk acoustic wave resonator according to an embodiment of the present disclosure. As shown in FIG. 5b, the first air gap 41 not only penetrates the piezoelectric layer 12 and the first electrode 11, but also penetrates part of the thickness of the substrate 10. The depth of the first air gap 41 penetrating the substrate is less than the depth of the first groove 102. That is, the distance from the bottom of the first air gap 41 to the second surface of the substrate 10 is greater than the distance from the bottom of the first groove 102 to the second surface of the substrate 10.

[0097] Further, the width of the first air gap 41 is about 1-2 μm, the width of the second air gap 42 is about 5-8 μm, and the depth of the first groove 102 is about 2-4 μm.

[0098] Further, the first air gap 41 has a certain spacing between the first groove 102 and the plane where the second surface of the substrate 10 is located. The spacing is about 0.5-3 μm.

[0099] In some examples, there are multiple first air gaps 41, and the multiple first air gaps 41 are arranged around the transition zone. Of course, the number of first air gaps 41 can also be one, or be set according to the size of the product.

[0100] In some examples, the bulk acoustic wave resonator further comprises at least one release hole 20 penetrating through the piezoelectric layer 12 and the first electrode 11 along the thickness direction of the substrate 10; the release hole 20 is located in the peripheral region. Wherein, FIG. 6 is a top view of the first slot part of the bulk acoustic wave resonator according to the embodiment of the present disclosure; as shown in FIG. 6, the first slot part 102 comprises a first sub-slot part 1021 located in the working region Q1 and the transition region Q3, and at least one second sub-slot part 1022 located in the peripheral region Q2; the first sub-slot part 1021 communicates with the second sub-slot part 1022, and the orthographic projection of one second sub-slot part 1022 and one release hole 20 on the plane where the second surface is located at least partially overlaps.

[0101] It should be noted that, in order to form other film layers of the bulk acoustic wave resonator on the substrate 10 with the first slot part 102, it is necessary to temporarily fill the first slot part 102 with a sacrificial layer, and remove the sacrificial layer after forming the other film layers, so it is necessary to form a sacrificial layer release hole on the other film layers for releasing the sacrificial layer. The specific process steps are described in detail in the subsequent preparation method.

[0102] Further, when the second sub-slot part 1022 is a plurality of, the plurality of second sub-slot parts 1022 are arranged at intervals along the circumferential direction of the first sub-slot part 1021. The second sub-slot part 1022 can be located at a part of the circumferential direction of the first sub-slot part 1021, or uniformly arranged around the first sub-slot part 1021.

[0103] Further, FIG. 7 is a top view of the first electrode of the bulk acoustic wave resonator according to the embodiment of the present disclosure; as shown in FIG. 7, the first electrode comprises a second main part 11a located in the working region Q1 and the transition region Q3, and at least one first auxiliary part 11b located in the peripheral region Q2; the first auxiliary part 11b is connected with the second main part 11a, and any two of the first auxiliary part 11b, the second sub-slot part 1022 and the release hole 20 orthographically project at least partially overlap on the plane where the second surface is located. Wherein, the position of the first auxiliary part 11b is used to form the sacrificial layer release hole 20. The formation of the first auxiliary part 11b includes but is not limited to a circle, a rectangle, a square, an ellipse, a triangle, a pentagon, a hexagon, a heptagon, etc.

[0104] In some examples, the first electrode 11, the piezoelectric layer 12 and the second electrode 13 of the embodiment of the present disclosure orthographically project on the plane where the second surface is located, and the overlapping area is circular, that is, the effective working area of the bulk acoustic wave resonator according to the embodiment of the present disclosure is circular.

[0105] In some examples, a mass load layer 16 can also be arranged on the side of the second electrode 13 away from the substrate 10. The mass load layer 16 can prevent water vapor and oxygen from entering the piezoelectric resonator, thereby preventing the performance of the piezoelectric resonator from deteriorating over time. In addition, when the frequency of the piezoelectric resonator deviates, the mass load layer 16 can be etched by local plasma to adjust and correct the frequency of the piezoelectric resonator to the desired value.

[0106] The mass load layer 16 can be made of inorganic materials such as SiNx, Al2O3, SiO2, AlN, BN, etc. that can prevent water vapor and oxygen from entering, or can be made of various metal materials (such as Mo, Al, Cu, Co, Ag, Ti, Pt, Ru, W, Au, Cr, Fe, Zn, Mg, Ni, Sn, Pb, Ce, Bi, Nb, Pd, Rh, Tl, Ir, U, Ta, Te, Th, V, Ba, Mn, Cd, Ge, Zr, Se, or an alloy of various metals or a stack of metal layers), or organic compounds such as polyimide, epoxy resin, etc. The mass load layer 16 can be a single layer of one material or a stack of multiple materials.

[0107] In some examples, the substrate 10 is preferably made of Si, or can be made of glass, sapphire, SiC, GaAs, GaN, InP, BN, ZnO, etc. The thickness of the substrate 10 can range from 0.1 um to 10 mm.

[0108] In some examples, the first electrode 11 is preferably made of Mo, or can be made of Al, Cu, Co, Ag, Ti, Pt, Ru, W, Au, Cr, Fe, Zn, Mg, Ni, Sn, Pb, Ce, Bi, Nb, Pd, Rh, Tl, Ir, U, Ta, Te, Th, V, Ba, Mn, Cd, Ge, Zr, Se, or an alloy of various metals or a stack of metal layers. The thickness of the first electrode 11 can range from 1 nm to 10 um.

[0109] In some examples, the piezoelectric layer 12 is preferably made of AlN, or can be made of Sc-doped AlN, BN, ZnO, PZT, GaN, InN, CdS, CdSe, ZnS, CdTe, ZnTe, GaAs, GaSb, InAs, InSb, GaSe, GaP, AlP, quartz crystal, LiTaO3, LiNbO3, La3Ga5SiO 14 BaTiO3, PbNb2O6, PBLN, LiGaO3, LiGeO3, TiGeO3, PbTiO3, PbZrO3, PVDF, etc. The piezoelectric layer 12 can be made of one piezoelectric material or a stack of various piezoelectric materials. The thickness of the piezoelectric layer 12 can range from 10 nm to 100 um.

[0110] In some examples, the second electrode 13 is preferably metal molybdenum, and can also be selected from Al, Cu, Co, Ag, Ti, Pt, Ru, W, Au, Cr, Fe, Zn, Mg, Ni, Sn, Pb, Ce, Bi, Nb, Pd, Rh, Tl, Ir, U, Ta, Te, Th, V, Ba, Mn, Cd, Ge, Zr, Se, and can also be an alloy material formed of various metals or a stack of metal layers. The thickness of the second electrode 13 ranges from 1 nm to 10 um.

[0111] The embodiment of the present disclosure further provides a preparation method of an example bulk acoustic wave resonator, which can include the following steps. FIG. 8 is a schematic diagram of an intermediate product formed by step S11 of the preparation method of the bulk acoustic wave resonator according to the embodiment of the present disclosure. FIG. 9 is a schematic diagram of an intermediate product formed by step S12 of the preparation method of the bulk acoustic wave resonator according to the embodiment of the present disclosure. FIG. 10 is a schematic diagram of an intermediate product formed by step S13 of the preparation method of the bulk acoustic wave resonator according to the embodiment of the present disclosure. FIG. 11 is a schematic diagram of an intermediate product formed by step S14 of the preparation method of the bulk acoustic wave resonator according to the embodiment of the present disclosure. FIG. 12 is a schematic diagram of an intermediate product formed by step S15 of the preparation method of the bulk acoustic wave resonator according to the embodiment of the present disclosure. FIG. 13 is a schematic diagram of an intermediate product formed by step S16 of the preparation method of the bulk acoustic wave resonator according to the embodiment of the present disclosure. FIG. 14 is a schematic diagram of an intermediate product formed by step S17 of the preparation method of the bulk acoustic wave resonator according to the embodiment of the present disclosure. FIG. 15 is a schematic diagram of an intermediate product formed by step S18 of the preparation method of the bulk acoustic wave resonator according to the embodiment of the present disclosure. FIG. 16 is a schematic diagram of an intermediate product formed by step S19 of the preparation method of the bulk acoustic wave resonator according to the embodiment of the present disclosure. FIG. 17 is a schematic diagram of an intermediate product formed by step S110 of the preparation method of the bulk acoustic wave resonator according to the embodiment of the present disclosure. FIG. 18 is a schematic diagram of an intermediate product formed by step S111 of the preparation method of the bulk acoustic wave resonator according to the embodiment of the present disclosure.

[0112] S11, providing a substrate 10, as shown in FIG. 8.

[0113] In some examples, the substrate 10 can be selected from a single crystal silicon substrate, and can also be selected from glass, quartz, sapphire, SiC, GaAs, GaN, InP, BN, ZnO, and the like. The thickness of the substrate 10 ranges from about 0.1 um to 10 mm.

[0114] For example, when the substrate 10 is a single crystal silicon substrate, the step S11 can include the following steps. First, the single crystal silicon substrate is cleaned by ultrasonic cleaning with deionized water. Then, the substrate is placed in a mixed solution of H2SO4:H2O=3:1 and heated to 250°C for 15 minutes. The substrate is then cleaned by ultrasonic cleaning with deionized water. Next, the substrate is placed in a mixed solution of NH4OH:H2O=1:6 and heated to 80°C for 15 minutes. The substrate is then cleaned by ultrasonic cleaning with deionized water. Next, the substrate is placed in a mixed solution of HCl:H2O2:H2O=1:1:5 and heated to 85°C for 15 minutes. The substrate is then cleaned by ultrasonic cleaning with HF:H2O=1:20 for 10 seconds to remove the surface oxide layer. Finally, the substrate is cleaned by ultrasonic cleaning with deionized water for 20 minutes, and then dried by a wind knife. Thus, the cleaning process of the substrate 10 is completed.

[0115] S12, forming a first groove portion 102 on the substrate 10, as shown in FIG. 9.

[0116] In some examples, the step S62 can include the following steps. First, a mask pattern is prepared on the substrate 10. Then, a photolithography process is performed, including coating (or spraying) glue, pre-baking, exposure, development, and post-baking. Next, an etching process is performed to form the first groove portion. The etching process can be wet etching or dry etching, and the wet etching is preferred. Finally, a glue removing process is performed to complete the preparation of the first groove portion 102.

[0117] S13, forming a sacrificial layer 100 in the first groove portion 102, as shown in FIG. 10.

[0118] In some examples, the material of the sacrificial layer 100 can be loose amorphous silicon dioxide doped with boron and phosphorus. The step S13 can include the following steps. First, a slurry containing loose amorphous silicon dioxide doped with boron and phosphorus is formed by any of the processes of plasma enhanced chemical vapor deposition (PECVD), sub-atmospheric chemical vapor deposition (SACVD), and screen printing. Then, the slurry is subjected to thermal annealing at 700-900°C for 15-30 minutes in a vacuum chamber. The thermal annealing causes the loose amorphous silicon dioxide doped with boron and phosphorus to liquefy and flow, completely filling the pores in the first groove portion and flowing flat. Then, the temperature is lowered for solidification. Finally, a chemical mechanical polishing process is performed. The substrate 10 is pressed against a rough polishing pad by a polishing head. With the coupling effect of the polishing liquid corrosion, the particle friction, and the polishing pad friction, the surface of the substrate 10 is planarized after a certain time. The material overflowing from the surface of the first groove portion is polished to a height equal to that of the surface of the substrate 10.

[0119] S14, forming a first electrode 11 on the side of the sacrificial layer 100 away from the substrate 10, as shown in FIG. 11.

[0120] In some examples, step S14 can include firstly performing full-area deposition of the metal thin film, and the deposition method is preferably direct current magnetron sputtering (radio frequency magnetron sputtering can also be used), and pulse laser sputtering (PLD), molecular beam epitaxy (MBE), thermal evaporation, electron beam evaporation, etc. can also be selected. Next, photolithography process is performed on the metal thin film, including glue coating (or glue spraying), pre-baking, exposure, development, post-baking. Finally, etching is performed, preferably wet etching process, or dry etching process can also be selected, to form a pattern of the first electrode 11.

[0121] S15, forming a piezoelectric layer 12 on the first electrode 11, as shown in FIG. 12.

[0122] In some examples, step S15 can include firstly performing orientation growth of the piezoelectric material, and the deposition method is preferably radio frequency magnetron sputtering. For AlN or Sc-doped AlN piezoelectric material, an Al target or an Al target + Sc target is selected as the target material, and by controlling Ar, N2 gas pressure and temperature during the deposition process and post-annealing time and temperature, a C-axis oriented AlN piezoelectric thin film or a Sc-doped AlN piezoelectric thin film is formed, preferably with a growth orientation of (001), or (100) and (111) orientations can also be used. The thin film deposition method can also be pulse laser sputtering (PLD), molecular beam epitaxy (MBE), metal organic chemical vapor deposition (MOCVD), plasma enhanced chemical vapor deposition (PECVD), etc. The piezoelectric layer 12 is deposited by full-area deposition, without photolithography and etching process.

[0123] S16, forming a first air gap 41 of a first sacrificial layer 61, as shown in FIG. 13.

[0124] In some examples, step S16 can include performing photolithography process, including glue coating (or glue spraying), pre-baking, exposure, development, post-baking. Preferably, dry etching process is used, or wet etching process can also be selected. Multi-step dry etching process is used, and the piezoelectric layer 12 is etched first to form the first air gap 41.

[0125] S17, forming a second sacrificial layer 62 located in the transition region Q3 and the peripheral region on the piezoelectric layer 12, as shown in FIG. 14.

[0126] In some examples, step S17 can include, first, deposition of the second sacrificial layer 62, preferably plasma enhanced chemical vapor deposition (PECVD), but also low pressure chemical vapor deposition (LPCVD), radio frequency magnetron sputtering, pulsed laser deposition (PLD), molecular beam epitaxy (MBE), metal organic chemical vapor deposition (MOCVD), thermal evaporation, electron beam evaporation. The second sacrificial layer 62 is subjected to a photolithography process, including coating (or spraying glue), pre-baking, exposure, development, post-baking. Finally, etching, preferably wet etching process, but also dry etching process, to form a pattern of the second sacrificial layer 62.

[0127] S18, preparing the second electrode 13 on the piezoelectric layer 12 and the second sacrificial layer 62, as shown in FIG. 15.

[0128] In some examples, step S18 can include, first, deposition of the second electrode 13, preferably direct current magnetron sputtering (radio frequency magnetron sputtering is also possible), but also pulsed laser deposition (PLD), molecular beam epitaxy (MBE), thermal evaporation, electron beam evaporation, etc. Next, the metal film is subjected to a photolithography process, including coating (or spraying glue), pre-baking, exposure, development, post-baking. Finally, etching, preferably wet etching process, but also dry etching process, to form a pattern of the second electrode 13.

[0129] S19, forming the mass loading layer 16 on the second electrode 13, as shown in FIG. 16.

[0130] In some examples, step S18 can include, first, deposition of the second electrode 13, preferably direct current magnetron sputtering (radio frequency magnetron sputtering is also possible), but also pulsed laser deposition (PLD), molecular beam epitaxy (MBE), thermal evaporation, electron beam evaporation, etc. Next, the metal film is subjected to a photolithography process, including coating (or spraying glue), pre-baking, exposure, development, post-baking. Finally, etching, preferably wet etching process, but also dry etching process, to form a pattern of the second electrode 13.

[0131] S110, releasing the second sacrificial layer 62 between the second electrode 13 and the piezoelectric layer 12 to form the second air gap 42, while releasing the second sacrificial layer 62 in the first air gap 41, as shown in FIG. 17.

[0132] In some examples, the boron and phosphorus doped silicon dioxide or boron doped loose silicon dioxide or phosphorus doped loose silicon dioxide film between the first electrode 11 and the piezoelectric layer 12 and in the first air gap 41 is completely etched away by a dry etching process in step S111.

[0133] S111, forming a release hole of the first sacrificial layer 61, as shown in FIG. 18.

[0134] In some examples, step S111 can include performing a photolithography process, including coating (or spraying glue), pre-baking, exposure, development, post-baking. A dry etching process is preferred, and a wet etching process can also be selected. A multi-step dry etching process is used, first etching the piezoelectric layer 12, changing the etching gas when etching to the first electrode 11 to continue etching the first electrode 11, and etching to the first sacrificial layer 61.

[0135] S112, etching and releasing the first sacrificial layer 61 in the first groove portion 102, as shown in FIG. 5a.

[0136] In some examples, the boron and phosphorus doped silicon dioxide or boron doped loose silicon dioxide or phosphorus doped loose silicon dioxide film between the substrate 10 and the support layer 14 is completely etched away by a dry etching process in step S112.

[0137] The above only gives an exemplary specific structure of a bulk acoustic wave resonator and a method for manufacturing the same. The bulk acoustic wave resonator of the present disclosure can also be any one of the structures in FIGS. 1, 3, and 4, with at least a first air gap extending through the piezoelectric layer and a second air gap located in the transition region Q3.

[0138] The present disclosure also provides a bulk acoustic wave filter composed of a plurality of electrically connected bulk acoustic wave resonators, which are any one of the bulk acoustic wave resonators described above.

[0139] In some examples, the bulk acoustic wave filter includes an input terminal and an output terminal, and a series branch and at least one parallel branch connected between the input terminal and the output terminal; the plurality of bulk acoustic wave resonators includes a plurality of first bulk acoustic wave resonators and at least one second bulk acoustic wave resonator.

[0140] The series branch includes a plurality of first bulk acoustic wave resonators connected in series between the input terminal and the output terminal; the parallel branch includes a second bulk acoustic wave resonator; one end of the second bulk acoustic wave resonator is connected to a first bulk acoustic wave resonator, and the other end is connected to a reference voltage terminal.

[0141] In one example, FIG. 19 is a circuit diagram of an example bulk acoustic wave filter according to embodiments of the present disclosure; as shown in FIG. 19. Embodiments of the present disclosure provide a bulk acoustic wave filter (P1-P5) including 5 first bulk acoustic resonators (S1-S5) and 5 second bulk acoustic resonators. Wherein the input end RF in of the bulk acoustic wave filter is directed to the output end RF out, the 5 first bulk acoustic resonators (S1-S5) are sequentially connected in series, and the 5 second bulk acoustic resonators (P1-P5) form 5 parallel branches. Specifically, the first electrode of the first first bulk acoustic resonator S1 is connected to the input end RF in, the second electrode of the first first bulk acoustic resonator S1 is connected to the second electrode of the first second bulk acoustic resonator P1 and the second electrode of the second first bulk acoustic resonator S2; the first electrode of the second bulk acoustic resonator is connected to the first electrode of the second second bulk acoustic resonator P2 and the first electrode of the third first bulk acoustic resonator S3; the second electrode of the third first bulk acoustic resonator S3 is connected to the second electrode of the third second bulk acoustic resonator P3 and the first electrode of the fourth first bulk acoustic resonator S4; the first electrode of the fourth first bulk acoustic resonator S4 is connected to the first electrode of the fourth second bulk acoustic resonator P4 and the first electrode of the fifth first bulk acoustic resonator S5; the second electrode of the fifth first bulk acoustic resonator S5 is connected to the output end RF out and the second electrode of the fifth second bulk acoustic resonator P5; the first electrode of the first second bulk acoustic resonator P1, the second electrode of the second second bulk acoustic resonator P2, the first electrode of the third second bulk acoustic resonator P3, the second electrode of the fourth second bulk acoustic resonator P4, and the first electrode of the fifth second bulk acoustic resonator P5 are all connected to the reference electrode.

[0142] It should be noted that the reference electrode in embodiments of the present disclosure can be specifically a ground terminal GND, which is only taken as an example in embodiments of the present disclosure.

[0143] In some examples, the 5 first bulk acoustic filters (S1-S5) and the 5 second bulk acoustic filters (P1-P5) are arranged in three rows; the second second bulk acoustic resonator P2, the fourth second bulk acoustic resonator P4, and the fifth first bulk acoustic resonator S5 are located in the first row; the first first bulk acoustic resonator S1, the second first bulk acoustic resonator S2, the fourth first bulk acoustic resonator S4, and the fifth second bulk acoustic resonator P5 are located in the second row; the first second bulk acoustic resonator P1, the third first bulk acoustic resonator S3, and the third second bulk acoustic resonator P3 are located in the third row. In this case, the structure of the bulk acoustic wave filter can be made more compact.

[0144] The sizes of at least some of the first bulk acoustic resonators in the five first bulk acoustic wave filters (S1-S5) are different, and the sizes of at least some of the second bulk acoustic resonators in the five second bulk acoustic wave filters (P1-P5) are different. The sizes of the five first bulk acoustic wave filters (S1-S5) and the five second bulk acoustic wave filters (P1-P5) are set reasonably to improve the compactness of the bulk acoustic wave filter.

[0145] Further, the average area of each first bulk acoustic resonator is smaller than the average area of each second bulk acoustic resonator. Simulation verification shows that the filtering effect of the bulk acoustic wave filter with the above setting is good.

[0146] In some examples, for the bulk acoustic wave filter described above, the substrate of each first bulk acoustic resonator and the substrate of each second bulk acoustic resonator are integrally formed. The bulk acoustic wave filter includes a first conductive layer, a semiconductor layer, and a second conductive layer arranged in sequence on the substrate. The first electrode of each first bulk acoustic resonator and the first electrode of each second bulk acoustic resonator are located in the first conductive layer; the piezoelectric layer of each first bulk acoustic resonator and the piezoelectric layer of each second bulk acoustic resonator are located in the semiconductor layer; and the second electrode of each first bulk acoustic resonator and the second electrode of each second bulk acoustic resonator are located in the second conductive layer. In this way, the bulk acoustic wave filter can be made thin and light, and the structure is simple and easy to manufacture.

[0147] Further, the first electrode of the second first bulk acoustic resonator S2 and the first electrode of the second second bulk acoustic resonator P2 are connected by a first connecting electrode 111; the first electrode of the second first bulk acoustic resonator S2 and the first electrode of the third first bulk acoustic resonator S3 are connected by a second connecting electrode 112; the first electrode of the fourth first bulk acoustic resonator S4 and the first electrode of the fourth second bulk acoustic resonator P4 are connected by a third connecting electrode 113; the first electrode of the fourth first bulk acoustic resonator S4 and the first electrode of the fifth first bulk acoustic resonator S5 are connected by a fourth connecting electrode 114; the first electrode of the first first bulk acoustic resonator S1 is connected with the input end RF in by a fifth connecting electrode 115; the first electrode of the first second bulk acoustic resonator P1 is connected with the reference electrode by a sixth connecting electrode 116; the first electrode of the third second bulk acoustic resonator P3 is connected with the reference electrode by a seventh connecting electrode 117; the first electrode of the fifth second bulk acoustic resonator P5 is connected with the reference electrode by an eighth connecting electrode 118. The second electrode of the first first bulk acoustic resonator S1 and the second electrode of the second first bulk acoustic resonator S2 are connected by a ninth connecting electrode 131; the second electrode of the first first bulk acoustic resonator S1 and the second electrode of the first second bulk acoustic resonator P1 are connected by a tenth connecting electrode 132; the second electrode of the third first bulk acoustic resonator S3 and the second electrode of the fourth first bulk acoustic resonator S4 are connected by an eleventh connecting electrode 133; the second electrode of the third first bulk acoustic resonator S3 and the second electrode of the third second bulk acoustic resonator P3 are connected by a twelfth connecting electrode 134; the second electrode of the fifth first bulk acoustic resonator S5 and the second electrode of the fifth second bulk acoustic resonator P5 are connected by a thirteenth connecting electrode 135; the second electrode of the second second bulk acoustic resonator P2 and the reference electrode are connected by a fourteenth connecting electrode 136; the second electrode of the fourth second bulk acoustic resonator P4 and the reference electrode are connected by a fifteenth connecting electrode 137; the second electrode of the fifth second bulk acoustic resonator P5 and the reference electrode are connected by a sixteenth connecting electrode 138.

[0148] Further, the first electrodes of the first bulk acoustic wave resonators (S1-S5) and the first electrodes of the second bulk acoustic wave resonators (P1-P5) are electrically connected to the connection electrodes located in the first conductive layer, that is, the first connection electrode 111, the second connection electrode 112, the third connection electrode 113, the fourth connection electrode 114, the fifth connection electrode 115, the sixth connection electrode 116, the seventh connection electrode 117, and the eighth connection electrode 118 are located in the first conductive layer. The second electrodes of the first bulk acoustic wave resonators (S1-S5) and the second electrodes of the second bulk acoustic wave resonators (P1-P5) are electrically connected to the connection electrodes located in the second conductive layer, that is, the ninth connection electrode 131, the tenth connection electrode 132, the eleventh connection electrode 133, the twelfth connection electrode 134, the thirteenth connection electrode 135, the fourteenth connection electrode 136, the fifteenth connection electrode 137, and the sixteenth connection electrode 138 are located in the second conductive layer.

[0149] In some examples, since the input end RF in, the output end RF out and the ground end in the bulk acoustic wave filter need to be connected with external signals, connection pads are further arranged on the first conductive layer and the second conductive layer for leading in the external signals. Specifically, the connection pads of the first conductive layer are respectively a first connection pad 121, a second connection pad 122, a third connection pad 123, a fourth connection pad 124, a fifth connection pad 125, a sixth connection pad 126 and a seventh connection pad 127. The second conductive layer further includes an eighth connection pad 141, a ninth connection pad 142, a tenth connection pad 143, an eleventh connection pad 144, a twelfth connection pad 145, a thirteenth connection pad 146 and a fourteenth connection pad 147. The first connection pad 121 is connected with the fifth connection electrode 115 and connected with the eighth connection pad 141 through a first connection via 1201 penetrating the semiconductor layer. The second connection pad 122 is connected with the ninth connection pad 142 through a second connection via 1202 penetrating the semiconductor layer, and the ninth connection pad 142 is connected with the fourteenth connection electrode 136. The third connection pad 123 is connected with the tenth connection pad 143 through a third connection via 1203 penetrating the semiconductor layer, and the tenth connection pad 143 is connected with the fifteenth connection electrode 137. The fourth connection pad 124 is connected with the eleventh connection pad 144 through a fourth connection via 1204 penetrating the semiconductor layer, and the eleventh connection pad 144 is connected with the sixteenth connection electrode 138. The fifth connection pad 125 is connected with the sixth connection electrode 116 and connected with the twelfth connection pad 145 through a fifth connection via 1205 penetrating the semiconductor layer. The sixth connection pad 126 is connected with the seventh connection electrode 117 and connected with the thirteenth connection pad 146 through a sixth connection via 1206 penetrating the semiconductor layer. The seventh connection pad 127 is connected with the eighth connection electrode 118 and connected with the fourteenth connection pad 147 through a seventh connection via 1207 penetrating the semiconductor layer.

[0150] Next, the structure of each film layer of the bulk acoustic wave resonator is described below in combination with the drawings.

[0151] In the drawings, FIG. 20 is a top view of a substrate of a bulk acoustic wave filter according to an embodiment of the present disclosure. As shown in FIG. 20, for the substrate of the bulk acoustic wave resonator, the substrate is provided with a first slot portion of a first bulk acoustic wave resonator and a first slot portion of a second bulk acoustic wave resonator. Since the first sacrificial layer is formed in the first slot portion, the pattern of the first slot portion is also the pattern of the first sacrificial layer.

[0152] Continuing to refer to FIG. 20, each first slot portion includes a first sub-slot portion 1021 and two second sub-slot portions 1022 connected to the first sub-slot portion 1021. The second sub-slot portions 1022 correspond to the positions of the first sacrificial layer release holes. In FIG. 20, the number of second sub-slot portions 1022 is two, but in a product, the number of second sub-slot portions 1022 can be one or more.

[0153] Further, in the embodiment of the present disclosure, the effective working area of the bulk acoustic wave resonator is circular, so the shape of the first sub-slot portion 1021 in the orthographic projection of the second surface of the substrate is circular. The shape of the orthographic projection of the second sub-slot portion 1022 on the second surface of the substrate can be various shapes, such as circular, rectangular, square, elliptical, triangular, pentagonal, hexagonal, heptagonal, etc.

[0154] In some examples, FIG. 21 is a top view of the first conductive layer of the bulk acoustic wave filter according to the embodiment of the present disclosure; as shown in FIG. 21, the first conductive layer includes the first electrodes of the first bulk acoustic wave resonators and the first electrodes of the second bulk acoustic wave resonators, a first connecting electrode 111, a second connecting electrode 112, a third connecting electrode 113, a fourth connecting electrode 114, a fifth connecting electrode 115, a sixth connecting electrode 116, a seventh connecting electrode 117, an eighth connecting electrode 118, a first connecting pad 121, a second connecting pad 122, a third connecting pad 123, a fourth connecting pad 124, a fifth connecting pad 125, a sixth connecting pad 126, and a seventh connecting pad 127.

[0155] The second connecting pad 122, the third connecting pad 123, and the fourth connecting pad 124 are independently provided. The first connecting pad 121, the fifth connecting electrode 115, and the first electrode of the first bulk acoustic wave resonator are connected as an integral structure. The fifth connecting pad 125, the sixth connecting electrode 116, and the first electrode of the first second bulk acoustic wave resonator P1 are connected as an integral structure. The sixth connecting pad 126, the seventh connecting electrode 117, and the first electrode of the third second bulk acoustic wave resonator P3 are connected as an integral structure. The seventh connecting pad 127, the eighth connecting electrode 118, and the first electrode of the fifth second bulk acoustic wave resonator P5 are connected as an integral structure.

[0156] Further, at least one of the first connecting electrode 111, the second connecting electrode 112, the third connecting electrode 113, the fourth connecting electrode 114, the fifth connecting electrode 115, the sixth connecting electrode 116, the seventh connecting electrode 117, and the eighth connecting electrode 118 has a line width that monotonically increases or monotonically decreases along the respective extension direction. In this way, it is convenient to route according to the spacing between the first electrodes. Of course, the line width of each connecting electrode can also be uniform.

[0157] In some examples, the first electrode can include a second main portion 11a and a first auxiliary portion 11b connecting the second main portion 11a, the first auxiliary portion 11b being disposed corresponding to the second sub-groove portion 1022. The second main portion 11a of the same bulk acoustic wave resonator can be concentric with the first sub-groove portion 1021 in the orthogonal projection on the plane of the second surface of the substrate, the orthogonal projection of the second main portion 11a on the plane of the second surface of the substrate can be larger than the orthogonal projection of the first sub-groove portion 1021 on the plane of the second surface of the substrate, and the radii of the two can differ by about 10 nm to 100 μm.

[0158] In some examples, the shapes of the first connection pad 121, the second connection pad 122, the third connection pad 123, the fourth connection pad 124, the fifth connection pad 125, the sixth connection pad 126, and the seventh connection pad 127 can all be squares, and the side length can be about 1 μm to 100 μm.

[0159] In some examples, FIG. 22 is a top view of a semiconductor layer of a bulk acoustic wave filter according to embodiments of the present disclosure; as shown in FIG. 22, the semiconductor layer includes a piezoelectric layer of each first bulk acoustic wave resonator and a piezoelectric layer of each second bulk acoustic wave resonator, and the piezoelectric layer of each first bulk acoustic wave resonator and the piezoelectric layer of each second bulk acoustic wave resonator are connected as an integral structure. The semiconductor layer further includes a first connection via hole 1201, a second connection via hole 1202, a third connection via hole 1203, a fourth connection via hole 1204, a fifth connection via hole 1205, a sixth connection via hole 1206, a seventh connection via hole 1207, a first through hole 1211, a second through hole 1212, a third through hole 1213, and a fourth through hole 1214. Among them, the first connection via hole 1201 is overlapped with the first connection pad 121 and the fifth connection electrode 115 in the normal projection of the second surface. The second connection via hole 1202 is overlapped with the second connection pad 122 in the normal projection of the second surface. The third connection via hole 1203 is overlapped with the third connection pad 123 in the normal projection of the second surface. The fourth connection via hole 1204 is overlapped with the fourth connection pad 124 in the normal projection of the second surface. The fifth connection via hole 1205 is overlapped with the sixth connection electrode 116 and the fifth connection pad 125 in the normal projection of the second surface. The sixth connection via hole 1206 is overlapped with the sixth connection pad 126 and the seventh connection electrode 117 in the normal projection of the second surface; the seventh connection via hole 1207 is overlapped with the seventh connection pad 127 and the eighth connection electrode 118 in the normal projection of the second surface. The first through hole 1211 is overlapped with the first connection electrode 111 in the normal projection of the second surface. The second through hole 1212 is overlapped with the second connection electrode 112 in the normal projection of the second surface. The third through hole 1213 is overlapped with the third connection electrode 113 in the normal projection of the second surface; the fourth through hole 1214 is overlapped with the fourth connection electrode 114 in the normal projection of the second surface. That is, by removing the pattern corresponding to the connection electrode and the connection pad in the first conductive layer from one semiconductor film, the semiconductor layer is formed.

[0160] In some examples, FIG. 23 is a top view of a second conductive layer of a bulk acoustic wave filter according to embodiments of the present disclosure; as shown in FIG. 23, the second conductive layer includes the second electrodes of the first bulk acoustic wave resonators and the second electrodes of the second bulk acoustic wave resonators, a ninth connection electrode 131, a tenth connection electrode 132, an eleventh connection electrode 133, a twelfth connection electrode 134, a thirteenth connection electrode 135, a fourteenth connection electrode 136, a fifteenth connection electrode 137, a sixteenth connection electrode 138, an eighth connection pad 141, a ninth connection pad 142, a tenth connection pad 143, an eleventh connection pad 144, a twelfth connection pad 145, a thirteenth connection pad 146, and a fourteenth connection pad 147.

[0161] In some examples, the second conductive layer includes the second electrodes of the first bulk acoustic wave resonators and the second electrodes of the second bulk acoustic wave resonators, and the projections of the second electrodes of each bulk acoustic wave resonator and the first sub-groove portion 1021 on the plane of the second surface of the substrate are concentric, and the radius of the projection of the second electrode of the bulk acoustic wave resonator on the plane of the second surface is smaller than the radius of the projection of the first sub-groove portion 1021 on the plane of the second surface, specifically smaller by about 10 nm to 100 um.

[0162] In some examples, the eighth connection pad 141, the twelfth connection pad 145, the thirteenth connection pad 146, and the fourteenth connection pad 147 are independently provided, the ninth connection pad 142, the fourteenth connection electrode 136, and the second electrode of the second bulk acoustic wave resonator P2 are connected as an integral structure; the tenth connection pad 143, the fifteenth connection electrode 137, and the second electrode of the fourth second bulk acoustic wave resonator P4 are connected as an integral structure; and the eleventh connection pad 144, the sixteenth connection electrode 138, and the second electrode of the fifth first bulk acoustic wave resonator S5 are connected as an integral structure.

[0163] The eighth connection pad 141 is connected to the first connection pad 121 through the first connection via hole 1201, the ninth connection pad 142 is connected to the second connection pad 122 through the second connection via hole 1202, the tenth connection pad 143 is connected to the third connection pad 123 through the third connection via hole 1203, the eleventh connection pad 144 is connected to the fourth connection pad 124 through the fourth connection via hole 1204, the twelfth connection pad 145 is connected to the fifth connection pad 125 through the fifth connection via hole 1205, the thirteenth connection pad 146 is connected to the sixth connection pad 126 through the sixth connection via hole 1206, and the fourteenth connection pad 147 is connected to the seventh connection pad 127 through the seventh connection via hole 1207.

[0164] In some examples, the eighth connection pad 141, the ninth connection pad 142, the tenth connection pad 143, the eleventh connection pad 144, the twelfth connection pad 145, the thirteenth connection pad 146, and the fourteenth connection pad 147 can each be square-shaped with a side length of about 1 μm to 100 μm.

[0165] In some examples, at least one of the ninth connection electrode 131, the tenth connection electrode 132, the eleventh connection electrode 133, the twelfth connection electrode 134, the thirteenth connection electrode 135, the fourteenth connection electrode 136, the fifteenth connection electrode 137, and the sixteenth connection electrode 138 has a line width that monotonically increases or monotonically decreases along the respective extension direction. In this way, it is convenient to wire according to the spacing between the respective first electrodes. Of course, the line width of each connection electrode can also be uniform. In the drawings, the line width of the tenth connection electrode 132, the eleventh connection electrode 133, the twelfth connection electrode 134, and the thirteenth connection electrode 135 is uniform, and the line width of the fourteenth connection electrode 136, the fifteenth connection electrode 137, and the sixteenth connection electrode 138 monotonically changes.

[0166] In some examples, FIG. 24 is a top view of the second sacrificial layer of the bulk acoustic wave filter according to an embodiment of the present disclosure; as shown in FIG. 24, the second air gap 42 of each first bulk acoustic wave resonator and the second air gap 42 of each second bulk acoustic wave resonator are each circular in orthographic projection on the second surface of the substrate. The inner radius of the second air gap 42 of each bulk acoustic wave resonator is smaller than the radius of the first sub-groove portion 1021, specifically by about 10 nm to 100 μm, and the outer radius of the second air gap 42 is larger than the radius of the second main body portion 11a of the first electrode, specifically by about 10 nm to 100 μm.

[0167] In some examples, the first air gap 41 of each first bulk acoustic wave resonator and the first air gap 41 of each second bulk acoustic wave resonator form a top view as shown in FIG. 25. The first air gap 41 can be provided in the manner shown in the drawings. The first air gap 41 can be multiple and can be arranged around the circumference of the second electrode. The diameter of the first air gap hole 41 is in the range of 10 nm to 10 μm, and the pitch of the holes is in the range of 10 nm to 10 μm.

[0168] The embodiments of the present disclosure also provide an electronic device, which can include any of the bulk acoustic wave filters described above.

[0169] It is understood that the above embodiments are only exemplary for illustrating the principles of the present application, and the present application is not limited thereto. Various modifications and improvements can be made by those skilled in the art without departing from the spirit and scope of the present application, and these modifications and improvements are also considered as the protection scope of the present application.

Claims

1. A bulk acoustic wave resonator, comprising: A substrate substrate, a first electrode, a piezoelectric layer and a second electrode are sequentially arranged on the substrate substrate; Any two of the first electrode, the piezoelectric layer and the second electrode at least partially overlap in the orthographic projection of the layer where the substrate substrate is located; wherein, The bulk acoustic wave resonator is divided into an operating area, a transition area surrounding the operating area, and a peripheral area surrounding the transition area; the bulk acoustic wave resonator comprises a first air gap and a second air gap located in the transition area; In the direction perpendicular to the substrate substrate, the first air gap at least penetrates part of the thickness of the piezoelectric layer; the second electrode comprises a first main part located in the operating area, and an edge part located in the transition area and connected with the first main part, the first main part is in contact with the piezoelectric layer, and the edge part has a gap with the piezoelectric layer to form the second air gap; The orthographic projection of the second air gap on the layer where the substrate substrate is located covers the orthographic projection of the first air gap on the layer where the substrate substrate is located.

2. The bulk acoustic resonator of claim 1, wherein, The substrate substrate has a first groove part; the substrate substrate comprises a first surface and a second surface oppositely arranged along the thickness direction thereof; the opening of the first groove part is located on the first surface, and the orthographic projection of the opening of the first groove part on the plane where the second surface is located is located in the orthographic projection of the first electrode on the plane where the second surface is located.

3. The bulk acoustic resonator of claim 2, wherein, The first air gap penetrates the piezoelectric layer, and part of the thickness of the first electrode and the substrate substrate; the depth of the first air gap penetrating the substrate substrate is smaller than the depth of the first groove part.

4. The bulk acoustic resonator of claim 2, wherein, Further comprising a support layer arranged between the first electrode and the first surface; the orthographic projection of the support layer on the plane where the second surface is located covers the orthographic projection of the opening of the first groove part on the plane where the second surface is located.

5. The bulk acoustic resonator of claim 2, wherein, The orthographic projection of the first air gap on the plane where the second surface is located has a certain spacing with the orthographic projection of the first groove part on the plane where the second surface is located.

6. The bulk acoustic resonator of claim 2, wherein, Further comprising at least one release hole penetrating the piezoelectric layer and the first electrode along the thickness direction of the substrate substrate; the release hole is located in the peripheral area; The first groove part comprises a first sub-groove part located in the operating area and the transition area, and at least one second sub-groove part located in the peripheral area; the first sub-groove part communicates with the second sub-groove part, and the orthographic projection of one of the second sub-groove parts and one of the release holes on the plane where the second surface is located at least partially overlaps.

7. The bulk acoustic resonator of claim 6, wherein, The first electrode comprises a second main part located in the operating area and the transition area, and at least one first auxiliary part located in the peripheral area; the first auxiliary part is connected with the second main part, and any two of the first auxiliary part, the second sub-groove part and the release hole at least partially overlap in the orthographic projection on the plane where the second surface is located.

8. The bulk acoustic resonator of claim 1, wherein, The first air gap is a plurality of first air gaps, and a plurality of first air gaps are arranged around the transition area.

9. The bulk acoustic resonator of any one of claims 1-8, wherein, The orthographic projection of the first electrode, the piezoelectric layer and the second electrode on the substrate substrate is circular in the overlapping area.

10. The bulk acoustic resonator of any one of claims 1-8, wherein, Further comprising a mass loading layer disposed on a side of the second electrode facing away from the substrate. 11.A bulk acoustic wave filter comprising a plurality of electrically connected bulk acoustic wave resonators; The bulk acoustic wave resonator adopts any one of the bulk acoustic wave resonators in claims 1-10.

12. The bulk acoustic wave filter of claim 11, wherein, The bulk acoustic wave filter comprises an input end and an output end, and a series branch and at least one parallel branch connected between the input end and the output end; A plurality of the bulk acoustic wave resonators comprise a plurality of first bulk acoustic wave resonators and at least one second bulk acoustic wave resonator; The series branch comprises a plurality of the first bulk acoustic wave resonators connected in series between the input end and the output end; The parallel branch comprises the second bulk acoustic wave resonator; One end of the second bulk acoustic wave resonator is connected to the first bulk acoustic wave resonator, and the other end is connected to a reference voltage end. The number of the first bulk acoustic wave resonators is 5, and the number of the second bulk acoustic wave resonators is 5; 13. The bulk acoustic wave filter of claim 12, wherein, The first electrode of the first bulk acoustic wave resonator is connected to the input end, and the second electrode of the first bulk acoustic wave resonator is connected to the second electrode of the first second bulk acoustic wave resonator and the second electrode of the second bulk acoustic wave resonator; The first electrode of the second bulk acoustic wave resonator is connected to the first electrode of the second second bulk acoustic wave resonator and the first electrode of the third first bulk acoustic wave resonator; The second electrode of the third first bulk acoustic wave resonator is connected to the second electrode of the third second bulk acoustic wave resonator and the first electrode of the fourth first bulk acoustic wave resonator; The first electrode of the fourth first bulk acoustic wave resonator is connected to the first electrode of the fourth second bulk acoustic wave resonator and the first electrode of the fifth first bulk acoustic wave resonator; The second electrode of the fifth first bulk acoustic wave resonator is connected to the output end and the second electrode of the fifth second bulk acoustic wave resonator; The first electrode of the first second bulk acoustic wave resonator, the second electrode of the second second bulk acoustic wave resonator, the first electrode of the third second bulk acoustic wave resonator, the second electrode of the fourth second bulk acoustic wave resonator and the first electrode of the fifth second bulk acoustic wave resonator are all connected to a reference electrode. The bulk acoustic wave filter comprises a first conductive layer, a semiconductor layer and a second conductive layer arranged in sequence in the direction away from the substrate; 14. The bulk acoustic wave filter of claim 13, wherein, The first electrode of each of the first bulk acoustic wave resonators and the first electrode of each of the second bulk acoustic wave resonators are located in the first conductive layer; The piezoelectric layer of each of the first bulk acoustic wave resonators and the piezoelectric layer of each of the second bulk acoustic wave resonators are located in the semiconductor layer; The second electrode of each of the first bulk acoustic wave resonators and the second electrode of each of the second bulk acoustic wave resonators are located in the second conductive layer. ​ 15. The bulk acoustic wave filter of claim 14, wherein, The first electrode of the second first bulk acoustic resonator and the first electrode of the second second bulk acoustic resonator are connected by a first connecting electrode; the first electrode of the second first bulk acoustic resonator and the first electrode of the third first bulk acoustic resonator are connected by a second connecting electrode; the first electrode of the fourth first bulk acoustic resonator and the first electrode of the fourth second bulk acoustic resonator are connected by a third connecting electrode; The first electrode of the fourth first bulk acoustic resonator and the first electrode of the fifth first bulk acoustic resonator are connected by a fourth connecting electrode; The first electrode of the first first bulk acoustic resonator is connected to the input terminal by a fifth connecting electrode; The first electrode of the first second bulk acoustic resonator is connected to the reference electrode by a sixth connecting electrode; The first electrode of the third second bulk acoustic resonator is connected to the reference electrode by a seventh connecting electrode; The first electrode of the fifth second bulk acoustic resonator is connected to the reference electrode by an eighth connecting electrode; The first connecting electrode, the second connecting electrode, the third connecting electrode, the fourth connecting electrode, the fifth connecting electrode, the sixth connecting electrode, the seventh connecting electrode, and the eighth connecting electrode are all located on the first conductive layer.

16. The bulk acoustic wave filter of claim 15, wherein, At least one of the first connecting electrode, the second connecting electrode, the third connecting electrode, the fourth connecting electrode, the fifth connecting electrode, the sixth connecting electrode, the seventh connecting electrode, and the eighth connecting electrode has a monotonically increasing or monotonically decreasing line width along the respective extension direction.

17. The bulk acoustic wave filter of claim 15, wherein, The second electrode of the first first bulk acoustic resonator and the second electrode of the second first bulk acoustic resonator are connected by a ninth connecting electrode; the second electrode of the first first bulk acoustic resonator and the second electrode of the first second bulk acoustic resonator are connected by a tenth connecting electrode; The second electrode of the third first bulk acoustic resonator and the second electrode of the fourth first bulk acoustic resonator are connected by an eleventh connecting electrode; the second electrode of the third first bulk acoustic resonator and the second electrode of the third second bulk acoustic resonator are connected by a twelfth connecting electrode; the second electrode of the fifth first bulk acoustic resonator and the second electrode of the fifth second bulk acoustic resonator are connected by a thirteenth connecting electrode; The second electrode of the second second bulk acoustic resonator and the reference electrode are connected by a fourteenth connecting electrode; the second electrode of the fourth second bulk acoustic resonator and the reference electrode are connected by a fifteenth connecting electrode; The second electrode of the fifth second bulk acoustic resonator and the reference electrode are connected by a sixteenth connecting electrode; The ninth connecting electrode, the tenth connecting electrode, the eleventh connecting electrode, the twelfth connecting electrode, the thirteenth connecting electrode, the fourteenth connecting electrode, the fifteenth connecting electrode, and the sixteenth connecting electrode are all located on the second conductive layer.

18. The bulk acoustic wave filter of claim 17, wherein, The line width of at least one of the ninth connection electrode, the tenth connection electrode, the eleventh connection electrode, the twelfth connection electrode, the thirteenth connection electrode, the fourteenth connection electrode, the fifteenth connection electrode and the sixteenth connection electrode monotonously increases or monotonously decreases along the respective extension direction.

19. The bulk acoustic wave filter of claim 17, wherein, The first conductive layer further comprises a first connection pad, a second connection pad, a third connection pad, a fourth connection pad, a fifth connection pad, a sixth connection pad and a seventh connection pad; The second conductive layer further comprises an eighth connection pad, a ninth connection pad, a tenth connection pad, an eleventh connection pad, a twelfth connection pad, a thirteenth connection pad and a fourteenth connection pad; The first connection pad is connected with the fifth connection electrode and connected with the eighth connection pad through a first connection via hole penetrating through the semiconductor layer; The second connection pad is connected with the ninth connection pad through a second connection via hole penetrating through the semiconductor layer, and the ninth connection pad is connected with the fourteenth connection electrode; The third connection pad is connected with the tenth connection pad through a third connection via hole penetrating through the semiconductor layer, and the tenth connection pad is connected with the fifteenth connection electrode; The fourth connection pad is connected with the eleventh connection pad through a fourth connection via hole penetrating through the semiconductor layer, and the eleventh connection pad is connected with the sixteenth connection electrode; The fifth connection pad is connected with the sixth connection electrode and connected with the twelfth connection pad through a fifth connection via hole penetrating through the semiconductor layer; The sixth connection pad is connected with the seventh connection electrode and connected with the thirteenth connection pad through a sixth connection via hole penetrating through the semiconductor layer; The seventh connection pad is connected with the eighth connection electrode and connected with the fourteenth connection pad through a seventh connection via hole penetrating through the semiconductor layer.

20. The bulk acoustic wave filter of claim 19, wherein, The first connection via hole has a projection on the plane of the second surface, which overlaps the projection of the first connection pad and the fifth connection electrode on the plane of the second surface; The second connection via hole has a projection on the plane of the second surface, which overlaps the projection of the second connection pad on the plane of the second surface; The third connection via hole has a projection on the plane of the second surface, which overlaps the projection of the third connection pad on the plane of the second surface; The fourth connection via hole has a projection on the plane of the second surface, which overlaps the projection of the fourth connection pad on the plane of the second surface; The fifth connection via hole has a projection on the plane of the second surface, which overlaps the projection of the sixth connection electrode and the fifth connection pad on the plane of the second surface; The sixth connection via hole has a projection on the plane of the second surface, which overlaps the projection of the sixth connection pad and the seventh connection electrode on the plane of the second surface; The seventh connection via hole has a projection on the plane of the second surface, which overlaps the projection of the seventh connection pad and the eighth connection electrode on the plane of the second surface; The semiconductor layer further comprises a first via, a second via, a third via and a fourth via penetrating through the semiconductor layer along a thickness direction of the semiconductor layer; A projection of the first via on a plane where the second surface is located overlaps with a projection of the first connection electrode on the plane where the second surface is located; A projection of the second via on a plane where the second surface is located overlaps with a projection of the second connection electrode on the plane where the second surface is located; A projection of the third via on a plane where the second surface is located overlaps with a projection of the third connection electrode on the plane where the second surface is located; A projection of the fourth via on a plane where the second surface is located overlaps with a projection of the fourth connection electrode on the plane where the second surface is located. 5 of the first SAW filters and 5 of the second SAW filters are arranged in three rows; 21. The bulk acoustic wave filter of any one of claims 13-20, wherein, The second second SAW resonator, the fourth second SAW resonator and the fifth first SAW resonator are located in the first row; The first first SAW resonator, the second first SAW resonator, the fourth first SAW resonator and the fifth second SAW resonator are located in the second row; The first second SAW resonator, the third first SAW resonator and the third second SAW resonator are located in the third row. An average area of each of the first SAW resonators is less than an average area of each of the second SAW resonators.

22. The bulk acoustic wave filter of any one of claims 13-20, wherein, 23. An electronic device comprising the SAW filter of any one of claims 11-22. ​

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