Bulk acoustic resonator and its assembly and fabrication method, electronic device, filter

Abstract

The present application discloses a bulk acoustic resonator and its assembly and fabrication method, electronic device, and filter, the bulk acoustic resonator includes a substrate, a first electrode with an acoustic reflection structure between the substrate, and a second electrode with a piezoelectric layer between the first electrode, the overlapping area of ​​the acoustic reflection structure, the first electrode, the piezoelectric layer, and the second electrode in a direction perpendicular to the substrate is an effective area, the effective area includes a first side and a second side arranged opposite to each other in a direction parallel to the substrate, the first free end and the second free end are connected to both ends of the first side and the second side to form a closed effective area, the extension length of the effective area between the first free end and the second free end is H, an arbitrary point on the first side is point A, the shortest distance from point A to the second side is D, and H / D>3. The heat dissipation efficiency of the resonator is improved by adjusting the extension length H of the resonator.

Description

[Technical field]

[0001] The present invention relates to the field of semiconductors, and more particularly to a bulk acoustic resonator, its assembly and fabrication method, electronic device, and filter. This application claims priority to a Chinese patent application filed with the China Patent Office on April 14, 2023, bearing application number 202310418733.6 and entitled "Bulk Acoustic Resonator and its Assembly and Fabrication Method, Electronic Device, and Filter", the entire contents of which are incorporated herein by reference. [Background technology]

[0002] Film bulk acoustic resonators (Fbar) have excellent characteristics such as small size (μ level), high resonance frequency (GHz), high quality factor (over 2000), large power capacity, and good roll-off effect, and play an important role in the radio frequency field of wireless communication. However, the central region of conventional resonators is far from the substrate at the edge of the resonator, and the central region is prone to heat accumulation, which causes temperature drift in the device, accelerating the aging of the device and causing it to expire, reducing reliability. Summary of the Invention [Problem to be solved by the invention]

[0003] Conventional methods for improving heat dissipation include increasing the thermal conductivity of the electrode or passivation layer material and increasing the heat dissipation coefficient of the substrate material. However, these methods are all indirect heat dissipation, and it is difficult to improve the heat dissipation effect. [Means for solving the problem]

[0004] In view of this, according to one aspect of the present application, there is provided a bulk acoustic resonator, the bulk acoustic resonator comprising: A substrate; a first electrode having an acoustic reflection structure between the first electrode and the substrate; a second electrode having a piezoelectric layer between the first electrode and the second electrode; In a direction perpendicular to the substrate, an overlapping area of ​​the acoustic reflection structure, the first electrode, the piezoelectric layer, and the second electrode is an effective area; In a direction parallel to the substrate, the effective area includes a first side and a second side arranged opposite each other, and both ends of the first side and the second side are connected by a first free end and a second free end so as to form a closed effective area, the extension length of the effective area between the first free end and the second free end is H, an arbitrary point on the first side is point A, the shortest distance from point A to the second side is D, and H / D>3.

[0005] Preferably, in the above bulk acoustic resonator, the shortest distances from the plurality of points A to the second side correspond to a plurality of Ds, the plurality of Ds have maximum and minimum values, and a ratio between the maximum and minimum values ​​is 1.5:1.

[0006] Preferably, in the above bulk acoustic resonator, the acoustic wave reflecting structure has a height in the range of 0.1 to 0.5 μm.

[0007] Preferably, in the bulk acoustic resonator, at least one of the first electrode, the piezoelectric layer, the second electrode and the acoustic reflection structure is the same as a projection of the active area on the substrate.

[0008] Preferably, in the above-mentioned bulk acoustic resonator, an effective area between the first free end and the second free end includes at least a first area, a second area, and a connecting portion, the first area and the second area are connected by the connecting portion, and the connecting portion includes a bending angle of more than 90 degrees and not more than 180 degrees or an arc-shaped connecting portion.

[0009] Preferably, in the above bulk acoustic resonator, the shape of the projection of the effective area on the substrate includes a U-shape, an S-shape, a W-shape, a spiral shape or a snake shape.

[0010] Preferably, in the above-mentioned bulk acoustic resonator, there are a first ineffective area and a second ineffective area outside the effective area, and in a direction perpendicular to the substrate, there is a gap between the piezoelectric layer and the second electrode and / or between the piezoelectric layer and the first electrode so as to form a first ineffective area.

[0011] Preferably, in the above bulk acoustic resonator, an upper surface of the first electrode and / or an upper surface of the piezoelectric layer has a first recess, and a first gap is present between at least one of the first recesses and the second electrode.

[0012] Preferably, in the above bulk acoustic resonator, the first electrode, or the first electrode and the piezoelectric layer, are recessed downward to form a second recess, and there is a second gap between at least one of the second recesses and the second electrode.

[0013] According to a second aspect of the present application, there is provided a resonator assembly comprising at least one bulk acoustic resonator as defined in any of the above, wherein said one bulk acoustic resonator is electrically connected to another bulk acoustic resonator and / or said one bulk acoustic resonator is electrically connected to at least one electrical structure.

[0014] Preferably, in the above bulk acoustic resonator assembly, at least a portion of the one bulk acoustic resonator is located within a space surrounded by an effective area of ​​the other bulk acoustic resonator.

[0015] Preferably, in the bulk acoustic resonator assembly, the bulk acoustic resonators share at least a portion of an effective area.

[0016] According to a third aspect of the present application, there is provided a filter, comprising a bulk acoustic resonator as defined in any one of the above.

[0017] According to a fourth aspect of the present application, there is provided an electronic device, comprising any of the bulk acoustic resonators described above.

[0018] According to a fifth aspect of the present application there is provided a method of fabricating a bulk acoustic resonator, said method comprising the steps of: Providing a substrate; forming an acoustic reflection structure on the substrate; forming a first electrode on a side of the acoustic reflecting structure away from the substrate; forming a piezoelectric layer on a side of the first electrode away from the substrate; forming a second electrode on a side of the piezoelectric layer away from the first electrode; In a direction perpendicular to the substrate, an overlapping area of ​​the acoustic reflection structure, the first electrode, the piezoelectric layer, and the second electrode constitutes an effective area; In a direction parallel to the substrate, the effective area includes a first side and a second side arranged opposite each other, and both ends of the first side and the second side are connected by a first free end and a second free end so as to form a closed effective area, the extension length of the effective area between the first free end and the second free end is H, an arbitrary point on the first side is point A, and the shortest distance from point A to the second side is D, where H / D>3.

[0019] Compared with the prior art, the beneficial effects achieved by the present invention are as follows: The bulk acoustic resonator has a strip-shaped effective area, which has a first side and a second side opposite to each other, and both ends of the first side and the second side are connected to a first free end and a second free end. The strip-shaped effective area can improve the heat dissipation efficiency of the resonator, so that the temperature of the resonator is basically constant in the operating state. The extension length of the strip-shaped effective area between the first free end and the second free end is H, and the shortest distance from point A, which is an arbitrary point on the first side, to the second side is D, and the heat dissipation efficiency of the resonator can be further enhanced by making H / D>3. In addition, the heat dissipation efficiency required for the resonator is positively correlated with the resonant frequency and the power allowance, so that the value of the ratio H / D can be further set according to the resonant frequency and the power allowance, which ensures that the resonator still has good heat dissipation efficiency and more stable performance under the condition of high frequency and high power allowance. In addition, compared with a conventional sandwich structure, the band-shaped effective area improves the force-bearing capacity of the resonator and increases the structural strength of the resonator. When the external vibration amplitude and vibration frequency are large, the resonator can still operate normally for a long time, thus greatly improving the mechanical stability of the resonator and ensuring a long operating life. [Brief description of the drawings]

[0020] In order to more clearly describe the technical solutions in the embodiments of the present invention or the prior art, the following briefly introduces drawings necessary for the description of the embodiments or the prior art. Obviously, the drawings in the following description are embodiments of the present invention, and those skilled in the art may obtain other drawings according to the drawings provided under the premise of not exerting any labor worthy of inventive step. The structures, proportions, sizes, etc. shown in the drawings in this specification are all intended to allow those skilled in the art to understand and read in accordance with the contents disclosed in the specification, and are not intended to limit the conditions under which the present invention is implemented, and therefore have no technically substantial meaning. Any modification of the structure, change in the ratio, or adjustment of the size is included within the scope of the technical content disclosed in the present invention as long as it does not affect the effects produced and the purpose achieved by the present invention. [Figure 1] FIG. 2 is a plan view of an air-gap bulk acoustic resonator. [Diagram 2] 2 is a cross-sectional view of the bulk acoustic resonator shown in FIG. 1 in the BB′ direction. [Diagram 3] FIG. 1 is a plan view of a bulk acoustic resonator provided by an embodiment of the present application. [Figure 4] 4 is a cross-sectional view of the bulk acoustic resonator shown in FIG. 3 in the MM′ direction. [Diagram 5] FIG. 4 is a plan view of a cavity of the bulk acoustic resonator shown in FIG. [Figure 6] FIG. 1 is a thermodynamic emulation diagram of a conventional sandwich-structure resonator. [Figure 7] FIG. 2 is a diagram of a thermodynamic emulation of a bulk acoustic resonator according to another embodiment of the present application. [Figure 8] FIG. 13 is a thermodynamic emulation diagram of another conventional sandwich structure resonator. [Figure 9] FIG. 2 is a diagram of a thermodynamic emulation of a bulk acoustic resonator provided by another embodiment of the present application. [Figure 10] 2 is a cross-sectional view of a bulk acoustic resonator according to another embodiment of the present application; [Figure 11] 2 is a cross-sectional view of a bulk acoustic resonator according to another embodiment of the present application; [Figure 12] FIG. 2 is a plan view of a bulk acoustic resonator provided by another embodiment of the present application. [Figure 13] 13 is a cross-sectional view of the bulk acoustic resonator shown in FIG. 12 in the NN′ direction. [Figure 14] FIG. 2 is a plan view of a bulk acoustic resonator provided by another embodiment of the present application. [Figure 15] 15 is a cross-sectional view of the bulk acoustic resonator shown in FIG. 14 in the FF′ direction. [Figure 16] FIG. 2 is a plan view of a resonator assembly provided by another embodiment of the present application. [Figure 17] FIG. 2 is a plan view of a resonator assembly provided by another embodiment of the present application. [Figure 18] FIG. 2 is a plan view of a resonator assembly provided by another embodiment of the present application. [Figure 19] FIG. 2 is a plan view of a resonator assembly provided by another embodiment of the present application. [Figure 20] FIG. 2 is a plan view of a resonator assembly provided by another embodiment of the present application. [Figure 21] FIG. 2 is a plan view of a resonator assembly provided by another embodiment of the present application. [Figure 22] FIG. 2 is a plan view of a resonator assembly provided by another embodiment of the present application. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] Hereinafter, the embodiments of the present application will be described clearly and completely in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, not all of them. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without creative labor are all within the scope of protection of the present application.

[0022] 1 and 2, FIG. 1 is a plan view of an air-gap type bulk acoustic resonator, and FIG. 2 is a cross-sectional view of the bulk acoustic resonator shown in FIG. 1 in the BB' direction, which includes a substrate 101', an acoustic reflection structure 102', a first electrode 103', a second electrode 105', and a piezoelectric layer 104' located between the two electrodes. The overlapping area of ​​the acoustic reflection structure 102', the first electrode 103', the piezoelectric layer 104', and the second electrode 105' is an effective area P'. The two electrodes are also called excitation electrodes, and their function is to induce mechanical vibration of the piezoelectric layer 104' of the resonator, and the acoustic reflection structure 102' effectively prevents the acoustic wave from being conducted out of the resonator and causing energy loss.

[0023] In an ideal state, the resonator realizes lossless conversion between mechanical energy and electrical energy, but in a practical situation, some electrical energy and bulk acoustic waves in the device will inevitably be converted into thermal energy, and the higher the power of the resonator, the more significant the heat generation effect. As shown in FIG. 2, the heat transfer path is shown by the dashed arrow, and since air is a poor thermal conductor, the resonator mainly transfers heat to the substrate 101' near the device through the device functional layer, i.e., the upper and lower electrodes and the piezoelectric layer 104', and then transfers heat from the substrate 101' near the device to the entire substrate 101' for heat dissipation. However, the central region O of the resonator is far from the substrate 101' at the edge of the resonator, and the central region O is prone to heat accumulation, so the device will have a temperature drift, which will promote the aging of the device, cause it to expire and reduce its reliability.

[0024] Conventional methods for enhancing heat dissipation include increasing the thermal conductivity of the electrode or passivation layer material, and increasing the heat dissipation coefficient of the substrate 101' material, but these methods are all indirect heat dissipation, and it is difficult to improve the heat dissipation effect. In addition, the electrodes need to adopt high acoustic impedance materials, so molybdenum (Mo), tungsten, ruthenium (Ru) or iridium (Ir) are preferred, and the preferred material for the piezoelectric layer 104' is generally aluminum nitride (AlN) or AlN doped with different proportions of scandium (Sc), i.e., AlScN. After years of research in the industry, the above materials are the most suitable Fbar device materials for mass production, so it is currently not practical to change the piezoelectric layer 104' or electrode materials. In order to improve the direct heat dissipation efficiency of the device, one method is to shorten the distance V from the central region O of the resonator to the substrate 101' in the direction parallel to the substrate 101' (this method is applied to above-ground and underground cavities, the above-ground cavity is located on the upper surface of the substrate 101', and the underground cavity is embedded inside the substrate 101'), thereby providing the shortest heat dissipation path and achieving the highest heat dissipation efficiency. However, simply shortening the distance V directly reduces the effective area of ​​the resonator, and the performance of the resonator does not meet the design requirements. Therefore, how to shorten the distance V from the central region O to the substrate 101' in the direction parallel to the substrate 101' and improve the heat dissipation efficiency under the premise of ensuring the performance of the device is a key technical issue.

[0025] Based on the above problems, this application provides a bulk acoustic resonator and its assembly and fabrication method, electronic device, and filter, in which the bulk acoustic resonator has a strip-shaped effective area, which improves the heat dissipation efficiency of the resonator and makes the temperature of the resonator basically constant when in operation, and the extension length of the effective area between the first free end and the second free end is H, an arbitrary point on the first side is point A, and the shortest distance from point A to the second side is D, and the extension length H is adjusted according to the resonant frequency and power tolerance of the resonator, so that H and D satisfy the relationship H / D>3, ensuring that the resonator still has good heat dissipation efficiency and more stable performance under the condition of high frequency and high power tolerance.

[0026] In order to make the above objectives, features and advantages of the present application clearer and easier to understand, the present application will be further described in detail below in combination with drawings and specific embodiments.

[0027] 3 and 4, FIG. 3 is a plan view of a bulk acoustic resonator provided by an embodiment of the present application, and FIG. 4 is a cross-sectional view of the bulk acoustic resonator shown in FIG. 3 in the MM′ direction. The bulk acoustic resonator includes a substrate 101, a first electrode 103 having an acoustic reflection structure 102 between it and the substrate 101, and a second electrode 105 having a piezoelectric layer 104 between it and the first electrode 103. In a direction perpendicular to the substrate 101, the acoustic reflection structure 102, the first electrode 103, the piezoelectric layer 104, and the second electrode 105 are arranged in a sectional view. The overlapping area is an effective area P, which includes a first side L1 and a second side L2 arranged opposite each other in a direction parallel to the substrate 101, and a first free end A1 and a second free end A2 are connected to both ends of the first side L1 and the second side L2 to form a closed effective area P, with the extension length of the effective area P between the first free end A1 and the second free end A2 being H, an arbitrary point on the first side L1 being point A, and the shortest distance from point A to the second side L2 being D, and H / D>3.

[0028] 3 and 4, the sound wave reflecting structure 102 includes a cavity 1021 or a Bragg reflecting layer, and in this embodiment, the sound wave reflecting structure 102 is taken as an example to be described as a cavity 1021. The effective area P in this embodiment is U-shaped, and it can be said that the U-shaped effective area is formed by bending the effective area P once. The effective area P in this embodiment can effectively improve the heat dissipation efficiency of the resonator based on its shape and size ratio, so that the temperature of the resonator is basically kept constant in the working state. In addition, according to the resonant frequency and power allowance needs of the resonator, the extension length H between the first free end A1 and the second free end A2 is adjusted, and H and the shortest distance D from the point A, which is an arbitrary point on the first side L1, to the second side L2 satisfy the relationship H / D>3, so as to ensure that the resonator still has good heat dissipation efficiency and more stable performance under the condition of high frequency and high power allowance. Since the distance from the central region of the resonator to the substrate is obviously reduced, compared with the normal sandwich structure, the moment of the central region is improved, and the amount of distortion of the functional layer of the resonator in this embodiment is greatly reduced under the same acting force, that is, the force that the resonator can withstand is increased, thus greatly enhancing the reliability of the film layer and effectively improving the mechanical stability of the device. Bending the active region of the resonator can maximize the reduction of the volume of the resonator and rationally utilize the space under the condition of ensuring that the resonator has high heat dissipation efficiency. In some embodiments, the shapes of the first side L1 and the second side L2 of the active region P are the same or different, and the shapes include, but are not limited to, straight lines, curved lines, or broken lines.

[0029] 3 and 5, FIG. 5 is a plan view of the cavity of the bulk acoustic resonator shown in FIG. 3, in which the resonator in this embodiment has a strip-shaped effective area P, and at least one of the first electrode 103, the piezoelectric layer 104, the second electrode 105, and the acoustic wave reflecting structure 102 is the same as the projection of the effective area P on the substrate 101.

[0030] 3 and 5, this embodiment takes as an example that the sound reflection structure 102 is an underground cavity 1021, the piezoelectric layer 104 is a membrane layer, the sound reflection structure 102, the second electrode 105 and the first electrode 103 are U-shaped, and the U-shaped structures of the sound reflection structure 102, the second electrode 105 and the first electrode 103 are preferably positioned in a direction perpendicular to the substrate 101. Moreover, the size of the U-shaped sound reflection structure 102 is larger than the U-shaped second electrode 105, that is, the shape of the sound reflection structure 102 is proportionally enlarged from the shape of the U-shaped effective area P. The substrate 101 includes 101a and 101b, the substrate 101a and the substrate 101b provide support for the resonator, and the resonator dissipates heat through two paths, the substrate 101a and the substrate 101b, i.e., compared with the normal cavity structure, the substrate 101b increases the heat transfer path, and further increases the heat dissipation efficiency of the resonator. When radio frequency signals are transmitted, the more the contact between the first electrode 103 and the surrounding medium, i.e., the larger the area of ​​the first electrode 103 above the substrate 101b, the larger the dielectric loss of the signal will be, or the higher the requirements for high impedance substrates will be, and the higher the cost will be. In this case, the first electrode 103 above 101b can be etched, i.e., the preferred first electrode 103 in this embodiment is a U-shaped structure, which reduces the contact area between the first electrode 103 and the substrate 101, thereby reducing the dielectric loss and improving the Q value of the resonator device.

[0031] Referring to FIG. 3, in the resonator of the above embodiment, the effective area P between the first free end A1 and the second free end A2 includes at least a first area, a second area, and a connection portion 109, the first area and the second area are connected by the connection portion 109, and the connection portion 109 includes a bending angle of more than 90 degrees and less than 180 degrees or an arc-shaped connection portion.

[0032] 3, the effective area P of the resonator in this embodiment includes two first areas, one second area, and two connecting parts 109, and the two first areas are connected to the same second area through the two connecting parts 109 to form a U-shaped effective area P, and the connecting parts 109 include a bending angle or arc-shaped connecting part that is greater than 90 degrees and less than 180 degrees, and the setting of the connecting parts 109 can be said to be setting the bending part of the U-shaped effective area P of the resonator at an obtuse angle or arc, which can increase the reflection path of the transverse wave and reduce the influence on the main vibration mode of the resonator after the transverse wave is superimposed, thereby reducing parasitics. In addition, the bending part of the cavity is obtuse angle or arc-shaped, which can reduce the influence on the resonator of the stress generated when the sacrificial layer is released.

[0033] Since the heat dissipation efficiency required for the resonator is positively correlated with the resonant frequency and power tolerance, the value of the H / D ratio can be set according to the resonant frequency and power tolerance to ensure that the resonator still has good heat dissipation efficiency under the conditions of high frequency and high power tolerance. For low, medium and high frequency resonators, any resonator with a band-shaped effective area can improve the heat dissipation efficiency, and the heat dissipation effect is more prominent especially for high frequency resonators.

[0034] FIG. 6 is a thermodynamic emulation diagram of a resonator with a normal sandwich structure, and FIG. 7 is a thermodynamic emulation diagram of a bulk acoustic resonator provided by another embodiment of the present application, in which the resonator with a normal sandwich structure shown in FIG. 6 has the same effective area and the same resonant frequency (medium-low frequency 2.5 GHZ) as the resonator shown in FIG. 7. As can be seen from the heat distribution of the normal sandwich structure shown in FIG. 6, the heat distribution of the normal sandwich structure is non-uniform, and the closer to the center region, the higher the temperature is, and the heat is accumulated in the center region, with the maximum temperature reaching 40.3°C. Compared with the normal sandwich structure, the heat distribution of the resonator shown in FIG. 7 is more uniform, and the maximum temperature is only 27.9°C, a difference of 12.4°C, which is better than the heat dissipation efficiency of the normal sandwich structure.

[0035] FIG. 8 is a thermodynamic emulation diagram of another ordinary sandwich-structured resonator, and FIG. 9 is a thermodynamic emulation diagram of a bulk acoustic resonator provided by another embodiment of the present application, where the other ordinary sandwich-structured resonator shown in FIG. 8 has the same effective area and the same resonant frequency as the resonator shown in FIG. 9 (high frequency 6GHZ). When the resonator works in a high frequency state, the thickness of the functional layer is thinner, so the heat dissipation efficiency is lower, and the thermal change is more obvious, and the maximum temperature at the center point of the other ordinary sandwich-structured resonator shown in FIG. 8 reaches 163°C. The maximum temperature of the resonator shown in FIG. 9 is only 76.9°C, and in the high frequency state, its temperature distribution is still relatively uniform, there is no obvious heat accumulation, and it reduces from 163°C to 76.9°C, and the difference reaches 86.1°C.

[0036] Due to the good heat dissipation effect of the resonator with a strip-shaped effective area, it is possible to ensure that the long-term operating temperature of the resonator is constant at room temperature or a slightly higher temperature, thereby increasing its operating lifetime, and its advantages are more obvious, especially for high-frequency resonators.

[0037] When the power tolerance of the resonator is constant, the resonant frequency has a positive correlation with the required heat dissipation efficiency, i.e., the higher the resonant frequency, the higher the heat dissipation efficiency required for the resonator, i.e., the larger the value of the ratio of H / D should be. For example, for an ordinary filter, the theoretical minimum power tolerance need is 26 dBm, i.e., 500 milliwatts, which can meet the needs of receiving, transmitting, and carrier aggregation of all 4G to 5G signals. However, in high frequency situations, such as 5 GHz, the heat generation effect of the resonator rises exponentially, and simple optimization can no longer guarantee the long-term reliability and performance stability of the product, and a specific structure needs to be designed, for example, when the resonant frequency is 5 GHz, D can be designed to be 25 to 35 μm and H can be designed to be 90 to 100 μm.

[0038] When the resonant frequency of the resonator is constant, the power allowance is positively correlated with the required heat dissipation efficiency, i.e., the higher the power allowance, the higher the heat dissipation efficiency required for the resonator, i.e., the larger the value of the H / D ratio should be. When the required filter power allowance needs are high, for example, the power allowance needs are 33 dBm, 37 dBm, and 40 dBm, i.e., 1 watt, 5 watts, and 10 watts, respectively, in this case, the structure of the resonator needs to be adjusted, for example, H / D is designed to be between 5 and 8, and the required heat dissipation efficiency is achieved by increasing the H / D ratio. For example, under the condition that the resonant frequency is 5 GHz, the power allowance is 500 milliwatts, and the effective area P is kept equal, H / D is set to 3. For example, under the condition that the resonant frequency is 5 GHz, the power allowance is 1 watt, and the effective area P is kept equal, H / D can be set to 6. As mentioned above, the design of the resonator can be adjusted comprehensively according to the performance, band, and power needs, and if a higher power budget is required, for example, 43 dBm, i.e., 20 watts, it can be realized by the above method. The power budget can be the power budget need of the filter or the power budget need of the resonator, and the parameters of the resonator can be adjusted according to the actual needs.

[0039] In the resonator of the above embodiment, the shortest distances from the multiple points A to the second side L2 correspond to multiple Ds, and the multiple Ds have maximum and minimum values, with the ratio of the maximum and minimum values ​​being 1.5:1.

[0040] In the above embodiment of the resonator, the effective area P has a first side L1 and a second side L2 arranged opposite to each other, an arbitrary point on the first side L1 is selected as point A, and the shortest distance from point A to the second side L2 is selected as D, and the number of points A on the first side L1 is several, and the shortest distance D from the several points A to the second side L2 also has several values ​​accordingly, and the ratio of the maximum value to the minimum value of the several values ​​is 1.5:1. Within the effective area P, 1 / 2 of the sum of the maximum distance and the minimum distance between the first free end A1 and the second free end A2 is H, and H / D>3. The size of H can be determined according to the shape of the first free end A1 and the second free end A2, the ends of the first free end A1 and the second free end A2 include, but are not limited to, a straight line, a broken line, or an arc shape, when the ends of the first free end A1 and the second free end A2 are straight lines, the length of H can be calculated from the ends of the free ends, in this case, H is half the sum of the lengths of the first side L1 and the second side L2. When the ends of the first free end A1 and the second free end A2 are broken lines or arc shapes, the lengths of the first free end A1 and the second free end A2 can be ignored, because compared with the extension length of the effective area P, the lengths of the first free end A1 and the second free end A2 are very short and can be ignored for convenience of calculation, so H can be further calculated by half the sum of the lengths of the first side L1 and the second side L2. On the premise of ensuring that the area of ​​the effective region P does not change, when H increases, the corresponding D / 2 is reduced, which effectively shortens the distance between the heat concentration region and the substrate 101, and further increases the heat dissipation efficiency. Furthermore, K=H / D can be defined as the heat dissipation index of the resonator device, and under the condition that the material of the substrate, the material of the electrode of the resonator, the material of the piezoelectric layer 104 of the resonator, the electrode of the resonator, the thickness of the piezoelectric layer 104, and the effective area of ​​the resonator do not change, the larger K is, the lower the working temperature of the resonator is, and preferably K>3.

[0041] In the resonator of the above embodiment, the height range of the sound wave reflecting structure 102 is 0.1 to 0.5 μm.

[0042] When the sound wave reflection structure 102 is a cavity 1021, in a normal situation, the height of the cavity 1021 is between 0.5-2 μm, and when the resonator resonates, the functional layer such as the upper first electrode 103 can be prevented from being connected to the substrate 101. In this embodiment, when the resonator achieves the required design area by designing the effective area A1, D can be designed small, and compared with the normal sandwich structure, the strain amount of the functional layer is greatly reduced under the same acting force, that is, the force that the resonator can withstand is increased, and thus the reliability of the film layer is greatly enhanced, and the height of the cavity 1021 is reduced to between 0.1-0.5 μm, in this case, the heat dissipation path is further shortened, and thus the heat dissipation efficiency of the resonator is further enhanced.

[0043] Regarding the cavity 1021 fitted inside the substrate 101, if the height of the cavity 1021 is increased, for example, to more than 0.5 μm, the height of the substrate 101 increases accordingly, and the distance over which the heat of the resonator is transferred from the upper surface of the substrate 101 to the lower surface of the substrate 101 increases, and the heat tends to accumulate in the vertical direction of the substrate 101, which is disadvantageous for heat dissipation. If the height of the cavity 1021 is smaller than 0.1 μm, the functional layer of the resonator may be connected to the substrate 101. In this embodiment, the height of the cavity 1021 is set to be 0.1 to 0.5 μm, and compared with the traditional cavity 1021, the height of the cavity 1021 is reduced, and the height of the substrate 101 can be reduced accordingly, so that the distance that the heat propagates in the vertical direction of the substrate 101 is reduced, and the heat is transferred to the bottom of the cavity 1021, i.e., along the horizontal direction of the substrate 101. By reducing the height of the cavity 1021, the resonator is converted from dissipating heat from both sides of the substrate 101 to dissipating heat from the bottom surface of the substrate 101, and the heat dissipation efficiency is greatly improved. Furthermore, the height of the cavity 1021 is reduced, which reduces the cost of depositing the sacrificial layer and shortens the release time.

[0044] In the above embodiment, when the acoustic reflection structure 102 is a Bragg reflection layer, there is direct contact between the Bragg reflection layer and the functional layer, and therefore the thinner Bragg reflection layer can reduce the thermal resistance between the functional layer and the underside of the substrate. Therefore, reducing the height to 0.1-0.5 μm can shorten the heat dissipation path, improve the heat dissipation efficiency, and reduce the manufacturing cost of the Bragg reflection layer.

[0045] 10 and 11, Fig. 10 is a cross-sectional view of a bulk acoustic resonator provided by another embodiment of the present application, and Fig. 11 is a cross-sectional view of a resonator provided by another embodiment of the present application. There are a first non-effective area C1 and a second non-effective area C2 outside the effective area P, and there is a gap between the piezoelectric layer 104 and the second electrode 105 and / or between the piezoelectric layer 104 and the first electrode 103 in a direction perpendicular to the substrate 101 to form the first non-effective area C1.

[0046] 10 and 11, a gap is provided between the piezoelectric layer 104 and the second electrode 105 and / or between the piezoelectric layer 104 and the first electrode 103 in a direction perpendicular to the substrate 101, so that a separation is formed between the film layers in the area corresponding to the gap, that is, the piezoelectric layer 104 in the area where the gap is located cannot contact at least the second electrode 105 or the first electrode 103 in a direction perpendicular to the substrate 101, so that no extra parasitic vibration is generated. Note that providing a gap in the resonator includes, but is not limited to, providing one or two gaps between two layers of the first electrode 103, the piezoelectric layer 104, and the second electrode 105 above the substrate 101 in the inner area of ​​the sound reflection structure 102, so as to form a first non-effective area C1 in the area. In this embodiment, a second non-effective area C2 is further included, and the second non-effective area C2 is an area other than the first non-effective area C1 and the effective area P.

[0047] As shown in FIG. 10 , in another embodiment of the present application, the upper surface of the first electrode 103 and / or the upper surface of the piezoelectric layer 104 has a first recess 1061, and there is a first gap 1071 between at least one of the first recesses 1061 and the second electrode 105.

[0048] 10, the sound wave reflecting structure 102 is U-shaped and embedded in the substrate 101. In the direction perpendicular to the substrate 101, the upper surface of the first electrode 103 has a first recess 1061, the piezoelectric layer 104 deposited on the first recess 1061 also forms a third recess 1062 with the shape of the first recess 1061 changing, and the second electrode 105 is deposited on the piezoelectric layer 104 across the third recess 1062, in this case, a first gap 1071 is formed between the third recess 1062 and the second electrode 105. In another modified embodiment, the upper surface of the first electrode 103 has a first recess 1061, and the piezoelectric layer 104 is grown horizontally across the first recess 1061, i.e., there is no recess on the upper surface of the piezoelectric layer, and a first gap 1071 is formed between the first recess 1061 and the piezoelectric layer 104. In another modified embodiment, the first electrode 103 is a film layer, there is no recess on its upper surface, and the first recess 1061 is directly formed on the piezoelectric layer 104 by a method such as etching, and the second electrode 105 is deposited on the piezoelectric layer 104 across the first recess 1061. Due to the separation of the first gap 1071, the second electrode 105 and the piezoelectric layer 104 cannot contact each other in a direction perpendicular to the substrate 101, and therefore no extra parasitic vibration is generated. In other embodiments, the central region of the first electrode 103 may be partially or completely etched to form a gap between it and the flatly grown piezoelectric layer 104 above, or the first electrode 103 may be etched to expose the surface of the substrate 101, to form a gap between the flatly grown piezoelectric layer 104 and the exposed surface of the substrate 101.

[0049] Referring to FIG. 11, the first electrode 103, or the first electrode 103 and the piezoelectric layer 104, are recessed downward to form second recessed portions 1063, and a second gap 1072 is formed between at least one of the second recessed portions 1063 and the second electrode 105, and the second gap 1072 is located in the first non-effective area C1.

[0050] 11, neither the first electrode 103 nor the piezoelectric layer 104 is subjected to processing such as etching, and the sound wave reflecting structure 102 is located on the surface of the substrate 101 and is sandwiched between the first electrode 103 and the substrate 101. That is, the first electrode 103 protrudes upward at the position of the effective region P and is recessed downward in the first non-effective region C1 to form a second recessed portion 1063, and the piezoelectric layer 104 and the second electrode 105 are grown flat above the second recessed portion 1063, thereby forming a second gap 1072 between the second recessed portion 1063 of the first electrode 103 and the piezoelectric layer 104. Alternatively, the first electrode 103 protrudes upward at the position of the effective region P and is recessed downward at the first non-effective region C1, and the piezoelectric layer 104 is directly grown on the first electrode 103 and recesses along with the recess of the first electrode 103, forming a second recess 1063 on the piezoelectric layer 104. In this case, a second gap 1072 is formed between the second recess 1063 of the piezoelectric layer 104 and the flatly grown second electrode 105, and the second gap 1072 is located in the first non-effective region C1. The sound wave reflection structure 102 is a cavity 1021. In this embodiment, the second gap 1072 separates the piezoelectric layer 104 and the second electrode 105 in the direction perpendicular to the substrate 101, so that the resonator at that location does not generate extra parasitic vibration. The above gap may be filled with air or a medium material, as long as the gap does not generate extra parasitic vibration in the area.

[0051] In the resonators of the above embodiments, the shape of the projection of the effective area P on the substrate 101 includes U-shape, S-shape, W-shape, spiral shape or snake shape.

[0052] In the situation where the heat dissipation efficiency is guaranteed, the effective area P is curved at least once to reduce the area of ​​the resonator to the maximum extent. On the premise that the effective area of ​​the resonator is kept unchanged, the resonator is arranged in a strip shape, the length H of the effective area P is increased, the width D of the effective area P is reduced, and the circumference of the resonator is further increased to improve its heat dissipation capability.

[0053] 12 and 13, Fig. 12 is a plan view of a bulk acoustic resonator provided in another embodiment of the present application, and Fig. 13 is a cross-sectional view of the bulk acoustic resonator in the direction N-N' shown in Fig. 12, in this embodiment, the effective area P is bent twice to form an S-shaped effective area P, the first free end A1 and the second free end A2 of the effective area P face different directions, the sound wave reflection structure 102, the first electrode 103 and the second electrode 105 are all S-shaped, and the piezoelectric layer 104 is a film layer. In the resonator of this embodiment, the sound wave reflection structure 102 is a cavity 1021.

[0054] 14 and 15, FIG. 14 is a plan view of a bulk acoustic resonator provided by another embodiment of the present application, and FIG. 15 is a cross-sectional view of the bulk acoustic resonator shown in FIG. 14 in the FF' direction. In this embodiment, the effective area P is bent three times to form a W-shaped effective area P, and the first free end A1 and the second free end A2 of the effective area P face the same direction, the sound wave reflection structure 102, the first electrode 103, and the second electrode 105 are all W-shaped, and the piezoelectric layer 104 is a film layer. In the resonator of this embodiment, the sound wave reflection structure 102 is a cavity 1021. Furthermore, the effective area P of the resonator may be bent more times to form a spiral or snake-shaped effective area, and of course, the snake-shaped effective area can be said to be formed by connecting multiple S-shaped effective areas.

[0055] Referring to FIG. 16, FIG. 16 is a plan view of a resonator assembly provided by another embodiment of the present application, based on the above resonator, another embodiment of the present application provides a resonator assembly including a resonator of any of the types of the above embodiments, wherein the bulk acoustic resonator of any of the types of the above embodiments is electrically connected to another bulk acoustic resonator, and / or the bulk acoustic resonator of any of the types of the above embodiments is electrically connected to at least one electrical structure 108.

[0056] Referring to FIG. 16, specifically, this embodiment presents a resonator assembly, which includes a resonator having a U-shaped active area P01 and an electrical structure 108. In the resonator assembly of this embodiment, the electrical structure 108 is connected to the center of the first non-active area C1 surrounded by the U-shaped active area P01, and the electrical structure 108 includes but is not limited to a capacitance (C), an inductance (L) and an LC circuit. The second electrode 105 (first electrode 103) of the active area P01 is connected to the outside, and the first electrode 103 (second electrode 105) in the first non-active area C1 is connected to one end of the capacitance (C), the inductance (L) and the LC circuit, and the capacitance (C), the inductance (L) and the LC circuit are electrically connected to the outside. The space of the central area is utilized rationally, and the overall size of the chip is reduced.

[0057] In some embodiments, the resonator assembly further includes at least two connected strip-shaped resonators, the strip-shaped resonators including at least one of a U-shape, a W-shape, a spiral shape, or a snake shape.

[0058] Referring to FIG. 17, FIG. 17 is a plan view of a resonator assembly provided by another embodiment of the present application, in which at least a portion of a bulk acoustic resonator of any of the types of the above embodiments is located within a space surrounded by an active area of ​​another bulk acoustic resonator.

[0059] 17, a resonator assembly provided in another embodiment of the present application will be described by taking as an example a resonator assembly formed by fitting two resonators each having a U-shaped effective area. In this embodiment, the first free end A1 and / or the second free end A2 of the effective area P02 are located inside the space surrounded by the effective area of ​​the effective area P03, that is, the first free end A1 and / or the second free end A2 of the effective area P03 are located within the first non-effective area C1 of the effective area P02, and the two effective areas are connected via the first connecting end I and the second connecting end Z. According to actual needs, the connection manner of the first connection end I and the second connection end Z is selected by determining that the relationship between the effective area P03 and the effective area P02 is parallel or series, and thus the connection manner of the first connection end I or the second connection end Z respectively includes: the second electrode 105 of the effective area P03 is connected to the second electrode 105 of the effective area P02, the first electrode 103 of the effective area P03 is connected to the first electrode 103 of the effective area P02, or the second electrode 105 of the effective area P03 is connected to the first electrode 103 of the effective area P02.

[0060] Referring to FIG. 18, FIG. 18 is a plan view of a resonator assembly provided in another embodiment of the present application. An example of a resonator assembly formed by fitting two resonators, both of which have S-shaped effective areas, is described. A part of the effective area P04 is located in the space surrounded by the effective area P05, and the two effective areas are connected through two connection ends, and the connection manner of the two connection ends is the same as the connection manner of the first connection end I and the second connection end Z in FIG. 17.

[0061] 19, which is a plan view of a resonator assembly provided by another embodiment of the present application, takes as an example a resonator assembly formed by fitting four resonators each having a U-shaped effective area, in which two free ends of the effective area P06 are located in the space surrounded by the effective area P07, two free ends of the effective area P07 are located in the space surrounded by the effective area P08, and two free ends of the effective area P08 are located in the space surrounded by the effective area P09, forming a resonator assembly fitted with a plurality of resonators. In addition, the four resonators are connected through connecting ends, and the connecting manner of the connecting ends is the same as that of the first connecting end I and the second connecting end Z in FIG. 17.

[0062] Another embodiment of the present application provides a resonator assembly in which multiple bulk acoustic resonators share at least a portion of an active area.

[0063] Referring to Fig. 20, Fig. 20 is a plan view of a resonator assembly provided by another embodiment of the present application, the resonator assembly of this embodiment is described as including two strip-shaped resonators, the resonator assembly includes an effective area P10 and an effective area P11, and the resonator assembly has a first shared effective area E1, and the effective area P10 and the effective area P11 are arranged to cross each other, and the shared effective area E1 is formed in the crossing area. The effective area P10 and the effective area P11 both satisfy the ratio relationship of H / D>3, thereby ensuring the heat dissipation efficiency of the resonator assembly, while reducing its volume and making reasonable use of space.

[0064] 21, which is a plan view of a resonator assembly provided by another embodiment of the present application, the resonator assembly of this embodiment is described as including three strip-shaped resonators, the resonator assembly includes an effective area P12, an effective area P13 and an effective area P14, and the resonator assembly has a second shared effective area E2, in other words, the effective area P12, the effective area P13 and the effective area P14 are arranged to cross each other, and a shared second effective area E2 is formed at the crossing area, and the crossing area is at any one free end of each effective area. The effective area P12, the effective area P13 and the effective area P14 all satisfy the ratio relationship of H / D>3.

[0065] 22, which is a plan view of a resonator assembly provided by another embodiment of the present application, the resonator assembly of this embodiment is described as including three strip-shaped resonators, the resonator assembly includes an effective area P15, an effective area P16 and an effective area P17, and the resonator assembly has a third shared effective area E3 and a fourth shared effective area E4, that is, the effective area P15, the effective area P16 and the effective area P17 are arranged to cross each other, and the third shared effective area E3 and the fourth shared effective area E4 are formed in the crossing area, and the shared effective area is formed in the center of the effective area of ​​each resonator. The above is only an example of the situation in which multiple strip-shaped resonators are connected, and the number of resonators and the number of shared effective areas can be adjusted according to the area of ​​the resonator and the heat dissipation efficiency of the resonator.

[0066] Based on the above embodiment, another embodiment of the present application further provides a filter, comprising a bulk acoustic resonator in the manner of any of the above embodiments, or comprising at least one resonator assembly as described above.

[0067] Based on the above embodiment, another embodiment of the present application further provides an electronic device, including a bulk acoustic resonator of any of the types of the above embodiments.

[0068] Based on the above embodiment, another embodiment of the present application further provides a method for fabricating a resonator.

[0069] 4, another embodiment of the present application provides a method for fabricating a bulk acoustic resonator, the method includes the steps of providing a substrate 101, forming an acoustic reflection structure 102 on the substrate 101, forming a first electrode 103 on a side of the acoustic reflection structure 102 that faces away from the substrate 101, forming a piezoelectric layer 104 on a side of the first electrode 103 that faces away from the substrate 101, and forming a second electrode 105 on a side of the piezoelectric layer 104 that faces away from the first electrode 103, and the acoustic reflection structure 102 is formed in a direction perpendicular to the substrate 101. 2. The overlapping area of ​​the first electrode 103, the piezoelectric layer 104, and the second electrode 105 constitutes an effective area P, and in a direction parallel to the substrate 101, the effective area P includes a first side L1 and a second side L2 arranged opposite each other, and both ends of the first side L1 and the second side L2 are connected to a first free end A1 and a second free end A2 so as to form a closed effective area P, and the extension length of the effective area P between the first free end A1 and the second free end A2 is H, an arbitrary point on the first side L1 is point A, and the shortest distance from point A to the second side L2 is D, where H / D>3. The preferred material of the substrate 101 is Si / sapphire / spinel, the acoustic reflection structure 102 includes a cavity 1021 or a Bragg reflection layer, the preferred material of the first electrode 103 is molybdenum (Mo), other possible materials are metal or alloy materials such as gold (Au), tungsten, copper (Cu), nickel (Ni), titanium (Ti), niobium (Nb), silver (Ag), tantalum (Ta), cobalt (Co) or aluminum (Al), etc. The preferred material of the piezoelectric layer 104 is aluminum nitride (AlN), and further possible materials include zinc oxide (ZnO), zinc sulfide (ZnS), lithium tantalate (LiTaO3), cadmium sulfide (CdS), lead titanate (PbTiO3), lead zirconate titanate (Pb(Zr,Ti)O3), etc. The preferred material of the second electrode 105 is molybdenum (Mo), and other selectable materials are metal or alloy materials such as gold (Au), tungsten, copper (Cu), nickel (Ni), titanium (Ti), niobium (Nb), silver (Ag), tantalum (Ta), cobalt (Co) or aluminum (Al). Materials of the substrate 101, the first electrode 103, the second electrode 105 and the piezoelectric layer 104 include, but are not limited to, the above materials.

[0070] Based on the above, it can be seen that the present application provides a bulk acoustic resonator and its assembly and fabrication method, electronic device, and filter, in which the bulk acoustic resonator has a strip-shaped effective area P, which improves the heat dissipation efficiency of the resonator and allows the temperature of the resonator to be kept essentially constant in the working state, and the extension length H of the effective area P between the first free end A1 and the second free end A2 is greater than the extension length between the first side L1 and the second side L2, an arbitrary point on the first side L1 is defined as point A, and the shortest distance from point A to the second side L2 is defined as D, and the extension length H is adjusted according to the needs of the resonator's resonant frequency and power tolerance, so that H and D satisfy the relationship H / D>3, which ensures that the resonator still has good heat dissipation efficiency and more stable performance under the condition of high frequency and high power tolerance, and the structural strength of the resonator is improved, and the mechanical stability of the device is greatly improved.

[0071] Each embodiment in this specification is described in a gradual or parallel or gradual and parallel combination, and each embodiment focuses on the difference from other embodiments, and the same or similar parts between each embodiment can be referred to each other. Since the resonator assembly, filter, electronic device and manufacturing method disclosed in the embodiment correspond to the structure of the resonator disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the description of the method part.

[0072] It should be understood that in the description of this application, the drawings and the description of the embodiments are explanatory, not limiting. Similar symbols throughout the specification and embodiments label similar structures. Also, for ease of understanding and description, the drawings may exaggerate the thickness of a layer, film, panel, region, etc. It should also be understood that when an element such as a layer, film, region, or base plate is referred to as being "on" or "on" another element, the element may be directly on the other element, or there may be an intermediate element. Also, "on" means that the element is positioned on or below another element, but does not essentially mean that the element is positioned on the top side of another element according to the direction of gravity.

[0073] The orientations or positional relationships indicated by the terms "upper", "lower", "top", "bottom", "inner", "outer", etc. are orientations or positional relationships shown based on the drawings, and are merely for convenience of explanation and simplicity of the present application, and are not intended to indicate or imply that the devices or elements referred to have a particular orientation and must be constructed and operated in a particular orientation, and therefore should not be understood as limiting the present application. When an assembly is identified as "connected" to another assembly, it can be directly connected to the other assembly, or there may be a centrally located assembly at the same time.

[0074] It should be further noted that, in this specification, terms such as "first" and "second" are used merely to distinguish an entity or operation from another entity or operation, and do not necessarily require or imply that such an entity relationship or ranking exists between the entities or operations. Furthermore, terms such as "comprise", "contains", or other variations thereof, imply non-exclusive inclusion. A product or device that includes a set of elements includes not only those elements, but also other elements not expressly listed, or further includes elements that were already present in such product or device. Without further limitation, an element defined by the phrase "comprises a..." does not exclude the presence of additional identical elements in a product or device that includes the above elements.

[0075] The above description of the disclosed embodiments enables one skilled in the art to realize or use the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Thus, the present application is not limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. 1. A bulk acoustic resonator comprising: A substrate; a first electrode having an acoustic reflection structure between the first electrode and the substrate; a second electrode having a piezoelectric layer between the first electrode and the second electrode; In a direction perpendicular to the substrate, an overlapping area of ​​the acoustic reflection structure, the first electrode, the piezoelectric layer, and the second electrode is an effective area; In a direction parallel to the substrate, the effective area includes a first side and a second side that are arranged opposite to each other, and both ends of the first side and the second side are connected to a first free end and a second free end so as to form a closed effective area, an extension length of the effective area between the first free end and the second free end is H, an arbitrary point on the first side is point A, and a shortest distance from the point A to the second side is D, and H / D>3. A bulk acoustic resonator comprising:

2. The shortest distances from the plurality of points A to the second side correspond to the plurality of points D, the plurality of points D have maximum and minimum values, and the ratio of the maximum value to the minimum value is 1.5:

1.

2. The bulk acoustic resonator of claim 1 .

3. The height range of the sound wave reflection structure is 0.1 to 0.5 μm; 2. The bulk acoustic resonator of claim 1 .

4. At least one of the first electrode, the piezoelectric layer, the second electrode, and the acoustic reflection structure is the same as a projection of the active area on the substrate.

2. The bulk acoustic resonator of claim 1 .

5. The effective area between the first free end and the second free end includes at least a first area, a second area, and a connecting portion, and the first area and the second area are connected by a connecting portion, and the connecting portion includes a bending angle or an arc-shaped connecting portion that is greater than 90 degrees and less than 180 degrees.

2. The bulk acoustic resonator of claim 1 .

6. The shape of the projection of the effective area on the substrate includes U-shape, S-shape, W-shape, spiral shape or snake shape; 2. The bulk acoustic resonator of claim 1 .

7. a first non-effective area and a second non-effective area are present outside the effective area, and a gap is present between the piezoelectric layer and the second electrode and / or between the piezoelectric layer and the first electrode in a direction perpendicular to the substrate so as to form a first non-effective area; 2. The bulk acoustic resonator of claim 1 .

8. an upper surface of the first electrode and / or an upper surface of the piezoelectric layer has a first recess, and a first gap is present between at least one of the first recesses and the second electrode; 8. The bulk acoustic resonator of claim 7.

9. the first electrode, or the first electrode and the piezoelectric layer, are recessed downward to form a second recess, and a second gap is present between at least one of the second recesses and the second electrode; 8. The bulk acoustic resonator of claim 7.

10. A resonator assembly comprising at least one bulk acoustic resonator according to any one of claims 1 to 9, said one bulk acoustic resonator being electrically connected to another bulk acoustic resonator and / or said one bulk acoustic resonator being electrically connected to at least one electrical structure.

13. A resonator assembly comprising:

11. at least a portion of the one bulk acoustic resonator is located within a space surrounded by an active area of ​​another bulk acoustic resonator; 11. The resonator assembly of claim 10.

12. The bulk acoustic resonators share at least a portion of an effective area.

11. The resonator assembly of claim 10.

13. A filter comprising a bulk acoustic resonator according to any one of claims 1 to 9. A filter characterized by:

14. An electronic device comprising the bulk acoustic resonator according to any one of claims 1 to 9.

1. An electronic device comprising:

15. 1. A method for fabricating a bulk acoustic resonator, comprising the steps of: Providing a substrate; forming an acoustic reflection structure on the substrate; forming a first electrode on a side of the acoustic reflecting structure away from the substrate; forming a piezoelectric layer on a side of the first electrode away from the substrate; forming a second electrode on a side of the piezoelectric layer away from the first electrode; In a direction perpendicular to the substrate, an overlapping area of ​​the acoustic reflection structure, the first electrode, the piezoelectric layer, and the second electrode constitutes an effective area; In a direction parallel to the substrate, the effective area includes a first side and a second side that are arranged opposite to each other, and both ends of the first side and the second side are connected to a first free end and a second free end so as to form a closed effective area, an extension length of the effective area between the first free end and the second free end is H, an arbitrary point on the first side is point A, and a shortest distance from the point A to the second side is D, where H / D>3. A method for fabricating a bulk acoustic resonator comprising the steps of:

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