Bulk acoustic wave resonator device and method of forming the same, filter device, and radio frequency front-end device

Abstract

A bulk acoustic wave resonator, its formation method, filtering device, and radio frequency front-end device are disclosed. The bulk acoustic wave resonator includes: a cavity; a first electrode layer, at least one end of which is located above or inside the cavity; a piezoelectric layer, with the cavity and the first electrode layer located on a first side of the piezoelectric layer; a second electrode layer located on a second side; a first passive structure located on the first side, having a first overlap with at least one edge of the first electrode layer; and a second passive structure located on the second side, having a second overlap with at least one edge of the second electrode layer. The first passive structure includes: a first raised portion located inside the resonant region; and a first extended portion located outside the resonant region, the first raised portion protruding relative to the first extended portion. The second passive structure includes: a second raised portion located inside the resonant region; and a second extended portion located outside the resonant region, the second raised portion protruding relative to the second extended portion. This invention suppresses parasitic edge modes and improves Z-strain. p And the corresponding Q value.

Description

Technical Field

[0001] This invention relates to the field of semiconductor technology, and more specifically, to a bulk acoustic wave resonator, a method for forming the same, a filtering device, and a radio frequency front-end device. Background Technology

[0002] Radio frequency (RF) front-end chips in wireless communication devices include: power amplifiers (PA), antenna switches, RF filters, multiplexers (including duplexers), and low-noise amplifiers (LNAs). Among these, RF filters include surface acoustic wave (SAW) filters, bulk acoustic wave (BAW) filters, micro-electro-mechanical system (MEMS) filters, and integrated passive device (IPD) filters.

[0003] SAW and BAW resonators have high quality factors (Q values). RF filters made from SAW and BAW resonators, characterized by low insertion loss and high out-band rejection, are the mainstream RF filters used in mobile phones, base stations, and other wireless communication equipment. The Q value is the quality factor of the resonator, defined as the center frequency divided by the resonator's 3dB bandwidth. SAW filters typically operate from 0.4GHz to 2.7GHz, while BAW filters typically operate from 0.7GHz to 7GHz.

[0004] As wireless communication technology evolves, the number of frequency bands used increases. Simultaneously, with the application of technologies such as carrier aggregation and frequency band stacking, mutual interference between wireless frequency bands becomes increasingly severe. High-performance BAW technology can solve the problem of mutual interference between frequency bands. With the advent of the 5G era, wireless mobile networks have introduced even higher communication frequency bands, and currently only BAW technology can solve the filtering problem of high-frequency bands.

[0005] Figure 1A BAW filter circuit is shown, comprising a trapezoidal circuit composed of multiple BAW resonators. The first terminal of the circuit is connected to a transceiver terminal, and the second terminal is connected to an antenna. Here, f1, f2, f3, and f4 represent four different frequencies. Within each BAW resonator, alternating positive and negative voltages are generated on the metal electrodes on both sides of the piezoelectric layer. The piezoelectric layer generates sound waves through these alternating voltages, and the sound waves propagate perpendicularly along the thickness direction of the piezoelectric layer within the resonator. For resonance to occur, the sound waves need to undergo total internal reflection at the upper surface of the upper metal electrode and the lower surface of the lower metal electrode to form standing sound waves. The condition for sound wave reflection is that the acoustic impedance of the contact area with the upper surface of the upper metal electrode and the lower surface of the lower metal electrode differs significantly from the acoustic impedance of the metal electrodes themselves.

[0006] The performance of an RF filter depends on the performance of the resonator, which is determined by the resonator's minimum series impedance Z. s Maximum parallel impedance Z p and electromechanical coupling factor Kt 2 The parameters are represented as follows, where Z s and Z p This refers to the electrical losses in a resonator, such as thermal losses and acoustic losses. The resonator operates at its series resonant frequency f. s When the input impedance is at its minimum, it reaches Z. s The resonator operates at the parallel resonant frequency f. p At this time, the input impedance value is at its maximum, reaching Z. p Electromechanical coupling coefficient Kt 2 Z represents s With Z p The frequency difference between them affects the passband bandwidth of the RF filter. A higher Kt value results in a lower passband bandwidth. 2 or Z p and lower Z s The resonator exhibits good performance. Those skilled in the art are aware that resonator design requires Kt... 2 With Z p Make a trade-off between them, that is, increase Kt 2 It will also reduce Z. p Improve Z p It will also reduce Kt 2 .

[0007] A film bulk acoustic wave resonator (FBAR) is a BAW resonator that can confine acoustic wave energy within a device. The resonant region of this resonator is above a vacuum or air and below a cavity. Because the acoustic impedance of the vacuum or air is significantly different from that of the metal electrodes, the acoustic waves can be reflected from the upper surface of the upper metal electrode and the lower surface of the lower metal electrode, forming standing waves.

[0008] Figure 2 A schematic diagram of an FBAR 200 is shown. The FBAR 200 includes: a substrate 201; a cavity 203 embedded in the substrate 201; a first electrode layer 205 (i.e., the lower electrode layer) located on the substrate 201 and the cavity 203, covering the cavity 203; a piezoelectric layer 207 located on the first electrode layer 205; and a second electrode layer 209 (i.e., the upper electrode layer) located on the piezoelectric layer 207; the overlapping region of the first electrode layer 205, the piezoelectric layer 207, and the second electrode layer 209 is the resonant region of the FBAR 200. Two sets of sound waves are generated within the resonant region. The first set includes compression waves and shear waves propagating along a direction perpendicular to the piezoelectric layer 207. The second set includes sound waves propagating toward the lateral edge of the piezoelectric layer 207, including Rayleigh-Lamb waves (RL waves), which propagate along the side surfaces of the two electrode layers to the lateral edge of the piezoelectric layer 207, exciting a spurious lateral mode at the edge and generating parasitic resonance, thereby reducing Z. p And the corresponding Q value. Summary of the Invention

[0009] The problem solved by this invention is to provide a bulk acoustic resonator and its formation method, a filtering device, and a radio frequency front-end device to attenuate the laterally propagating acoustic waves generated in the resonant region, suppress parasitic edge modes, and improve Z-sound quality. p and the corresponding Q value, while also considering Kt 2 The impact is relatively small.

[0010] To address the aforementioned problems, the present invention provides a bulk acoustic resonator, comprising: a cavity; a first electrode layer, at least one end of which is located above or within the cavity; a piezoelectric layer, comprising a first side and a second side perpendicular to the first side, the cavity being located on the first side, the first electrode layer being located on the first side, and the first electrode layer contacting the piezoelectric layer; a second electrode layer, located on the second side and contacting the piezoelectric layer, wherein the overlapping region of the first electrode layer, the second electrode layer, and the piezoelectric layer is a resonant region; a first passive structure, located on the first side, having a first overlapping portion with at least one edge of the first electrode layer; and a second passive structure, located on the second side, having a second overlapping portion with at least one edge of the second electrode layer; wherein the first passive structure includes: a first raised portion, located inside the resonant region, having the first overlapping portion with at least one edge of the first electrode layer, the first raised portion being used to match the acoustic impedance of the resonant region with at least one attenuation region outside the resonant region, so that more The acoustic waves generated within the resonant region enter at least one of the attenuation regions; a first dielectric portion, located between the first raised portion and the first electrode layer, is used to electrically isolate the first electrode layer from the first passive structure; a first extension portion, located outside the resonant region and within at least one of the attenuation regions, is used to attenuate acoustic waves entering at least one of the attenuation regions, the first raised portion protruding relative to the first extension portion; the second passive structure includes: a second raised portion, located inside the resonant region, having a second overlapping portion with at least one edge of the second electrode layer, the second raised portion being used to match the acoustic impedance of the resonant region and at least one of the attenuation regions, allowing more acoustic waves generated within the resonant region to enter at least one of the attenuation regions; a second dielectric portion, located between the second raised portion and the second electrode layer, is used to electrically isolate the second electrode layer from the second passive structure; a second extension portion, located outside the resonant region and within at least one of the attenuation regions, is used to attenuate acoustic waves entering at least one of the attenuation regions, the second raised portion protruding relative to the second extension portion.

[0011] Optionally, the first passive structure and the second passive structure surround the resonant region.

[0012] Optionally, the thickness of the first passive structure is equal to or less than the thickness of the first electrode layer, and the thickness of the second passive structure is equal to or less than the thickness of the second electrode layer.

[0013] Optionally, at least one of the attenuation regions includes a first attenuation region, the first cutoff frequency of the first attenuation region being equal to or less than the cutoff frequency of the resonant region, and the first attenuation region corresponding to the overlapping area of ​​the first extension, the piezoelectric layer, and the second extension.

[0014] Optionally, it further includes: a first electrode extension layer located on the first side and connected to the first electrode layer; and a second electrode extension layer located on the second side and connected to the second electrode layer.

[0015] Optionally, at least one of the attenuation regions includes a second attenuation region, the second cutoff frequency of which is equal to or less than the cutoff frequency of the resonant region, and the second attenuation region corresponds to the overlapping region of the second electrode extension layer, the piezoelectric layer, and the first extension.

[0016] Optionally, at least one of the attenuation regions includes a third attenuation region, the third cutoff frequency of which is equal to or less than the cutoff frequency of the resonant region, and the third attenuation region corresponds to the overlapping region of the second extension, the piezoelectric layer, and the first electrode extension layer.

[0017] Optionally, at least one edge of the first electrode layer is sloped down, corresponding to the first passive structure, and at least one edge of the second electrode layer is sloped down, corresponding to the second passive structure.

[0018] Optionally, the width of the first raised portion is an integer multiple of half the wavelength of the sound wave generated in the resonant region, and the width of the second raised portion is an integer multiple of half the wavelength of the sound wave generated in the resonant region.

[0019] Optionally, the thickness of the first extension is less than the thickness of the first electrode layer, and the thickness of the second extension is less than the thickness of the second electrode layer.

[0020] Optionally, the first extension includes a first sub-part and a second sub-part, the second sub-part and the piezoelectric layer being located on opposite sides of the first sub-part, and the material of the first sub-part being different from the material of the second sub-part.

[0021] Optionally, the second extension includes a third sub-part and a fourth sub-part, with the piezoelectric layer and the fourth sub-part located on opposite sides of the third sub-part, and the material of the third sub-part being different from that of the fourth sub-part.

[0022] Optionally, the first extension contacts the piezoelectric layer, and the second extension contacts the piezoelectric layer.

[0023] Optionally, the first dielectric portion is also located between the piezoelectric layer and the first extension portion, and the second dielectric portion is also located between the piezoelectric layer and the second extension portion.

[0024] Optionally, a first slot is included between the first extension and the piezoelectric layer, and a second slot is included between the piezoelectric layer and the second extension.

[0025] Optionally, it further includes: a third dielectric portion located on the second side and in contact with the second electrode layer; and a surrounding groove located within the third dielectric portion, inside the resonant region, inside the second raised portion, and adjacent to the second raised portion.

[0026] Optionally, the shape of the circumferential groove includes: circular, elliptical, or polygonal.

[0027] Optionally, it further includes: a third dielectric portion located on the first side and in contact with the first electrode layer; and a surrounding groove located within the third dielectric portion, inside the resonant region, inside the first raised portion, and adjacent to the first raised portion.

[0028] Optionally, the shape of the circumferential groove includes: circular, elliptical, or polygonal.

[0029] Accordingly, the present invention also provides a filtering device, including: at least one bulk acoustic resonator as described above.

[0030] Accordingly, the present invention also provides a radio frequency front-end device, comprising: a power amplifier and at least one filter as described above; the power amplifier and the filter are connected.

[0031] Accordingly, the present invention also provides a radio frequency front-end device, characterized in that it includes: a low-noise amplifier and at least one filtering device as described above; the low-noise amplifier is connected to the filtering device.

[0032] Accordingly, the present invention also provides a radio frequency front-end device, characterized in that it includes: a multiplexing device, wherein the multiplexing device includes at least one filtering device as described above.

[0033] Accordingly, the present invention also provides a method for forming a bulk acoustic resonant device, comprising: forming a piezoelectric layer, the piezoelectric layer including a first side and a second side perpendicular to the first side in a vertical direction; forming a first electrode layer located on the first side and in contact with the piezoelectric layer; forming a second electrode layer located on the second side and in contact with the piezoelectric layer, wherein the overlapping area of ​​the first electrode layer, the second electrode layer and the piezoelectric layer is a resonant region; forming a first passive structure located on the first side and having a first overlapping portion with at least one edge of the first electrode layer; wherein the first passive structure includes: a first raised portion, a first extended portion and a first dielectric portion, the first raised portion protruding relative to the first extended portion; wherein the first raised portion is located inside the resonant region and has the first overlapping portion with at least one edge of the first electrode layer, the first raised portion being used to match the acoustic impedance of the resonant region and at least one attenuation region outside the resonant region, so that more sound waves generated in the resonant region enter at least one attenuation region; the first dielectric portion is located between the first raised portion and the first electrode layer. Between the electrode layers, the first electrode layer and the first passive structure are electrically isolated; the first extension is located outside the resonant region and within at least one of the attenuation regions, used to attenuate sound waves entering at least one of the attenuation regions; a second passive structure is formed, located on the second side, having a second overlap with at least one edge of the second electrode layer, wherein the second passive structure includes: a second raised portion, a second extension portion, and a second dielectric portion, the second raised portion protruding relative to the second extension portion; wherein the second raised portion is located inside the resonant region and has a second overlap with at least one edge of the second electrode layer, the second raised portion is used to match the acoustic impedance of the resonant region and at least one of the attenuation regions, allowing more sound waves generated in the resonant region to enter at least one of the attenuation regions; the second dielectric portion is located between the second raised portion and the second electrode layer, used to electrically isolate the second electrode layer and the second passive structure; the second extension portion is located outside the resonant region and within at least one of the attenuation regions, used to attenuate sound waves entering at least one of the attenuation regions.

[0034] Optionally, the first passive structure and the second passive structure surround the resonant region.

[0035] Optionally, the thickness of the first passive structure is equal to or less than the thickness of the first electrode layer, and the thickness of the second passive structure is equal to or less than the thickness of the second electrode layer.

[0036] Optionally, forming the first electrode layer includes forming at least one downsloping edge corresponding to the first passive structure, and forming the second electrode layer includes forming at least one downsloping edge corresponding to the second passive structure.

[0037] Optionally, forming the first passive structure includes: forming a first passivation layer located on the first side and covering the first electrode layer; forming a first overlap layer in contact with the first passivation layer, wherein the first overlap layer and at least one edge of the first electrode layer have the first overlapping portion; wherein the first passivation layer includes the first dielectric portion; wherein the first overlap layer includes the first raised portion and the first extended portion.

[0038] Optionally, forming the second passive structure includes: forming a second passivation layer located on the second side and covering the second electrode layer; forming a second overlap layer in contact with the second passivation layer, wherein at least one edge of the second overlap layer and the second electrode layer has a second overlapping portion; wherein the second passivation layer includes a second dielectric portion; wherein the second overlap layer includes a second raised portion and a second extended portion.

[0039] Optionally, the thickness of the first extension is less than the thickness of the first electrode layer, and the thickness of the second extension is less than the thickness of the second electrode layer.

[0040] Optionally, at least one of the attenuation regions includes a first attenuation region, the first cutoff frequency of the first attenuation region being equal to or less than the cutoff frequency of the resonant region, and the first attenuation region corresponding to the overlapping area of ​​the first extension, the piezoelectric layer, and the second extension.

[0041] Optionally, it further includes: forming a first electrode extension layer located on the first side and connected to the first electrode layer; and forming a second electrode extension layer located on the second side and connected to the second electrode layer.

[0042] Optionally, at least one of the attenuation regions includes a second attenuation region, the second cutoff frequency of which is equal to or less than the cutoff frequency of the resonant region, and the second attenuation region corresponds to the overlapping region of the second electrode extension layer, the piezoelectric layer, and the first extension.

[0043] Optionally, at least one of the attenuation regions includes a third attenuation region, the third cutoff frequency of which is equal to or less than the cutoff frequency of the resonant region, and the third attenuation region corresponds to the overlapping region of the second extension, the piezoelectric layer, and the first electrode extension layer.

[0044] Optionally, the width of the first raised portion is an integer multiple of half the wavelength of the sound wave generated in the resonant region, and the width of the second raised portion is an integer multiple of half the wavelength of the sound wave generated in the resonant region.

[0045] Optionally, forming the first edge layer includes forming a first edge sub-layer and a second edge sub-layer, wherein the second edge sub-layer and the piezoelectric layer are located on opposite sides of the first edge layer, and the material of the first edge sub-layer is different from the material of the second edge layer.

[0046] Optionally, forming the second edge layer includes forming a third edge sub-layer and a fourth edge sub-layer, wherein the fourth edge sub-layer and the piezoelectric layer are located on opposite sides of the third edge layer, and the material of the third edge layer is different from that of the fourth edge layer.

[0047] Optionally, it further includes: forming a first sacrificial layer located between the first extension and the piezoelectric layer; and forming a second sacrificial layer located between the second extension and the piezoelectric layer.

[0048] Optionally, it further includes: removing the first sacrificial layer to form a first slot located between the first extension and the piezoelectric layer; and removing the second sacrificial layer to form a second slot located between the second extension and the piezoelectric layer.

[0049] Optionally, the first dielectric portion is also located between the piezoelectric layer and the first extension portion, and the second dielectric portion is also located between the piezoelectric layer and the second extension portion.

[0050] Optionally, it further includes: forming a third dielectric portion located on the second side and in contact with the second electrode layer; forming a surrounding groove located within the third dielectric portion, inside the resonant region, inside the second raised portion, and adjacent to the second raised portion.

[0051] Optionally, the shape of the circumferential groove includes: circular, elliptical, or polygonal.

[0052] Optionally, it further includes: forming a third dielectric portion located on the first side and in contact with the first electrode layer; forming a surrounding groove located within the third dielectric portion, inside the resonant region, inside the first raised portion, and adjacent to the first raised portion.

[0053] Optionally, the shape of the circumferential groove includes: circular, elliptical, or polygonal.

[0054] Compared with the prior art, the technical solution of the present invention has the following advantages:

[0055] In the bulk acoustic resonator of this invention, the first raised portion of the first passive structure is located inside the resonant region and overlaps with the first electrode layer; the second raised portion of the second passive structure is located inside the resonant region and overlaps with the second electrode layer. This allows for matching the acoustic impedance of the resonant region with that of the evanescent region outside the resonant region, thereby allowing more sound waves generated in the resonant region to propagate into the evanescent region. Furthermore, the cutoff frequency of the evanescent region matches (e.g., is equal to or less than) the cutoff frequency of the resonant region, which attenuates the sound waves entering the evanescent region, suppresses parasitic edge modes, and enhances Z-axis propagation. p and the corresponding Q value. The cutoff frequency is the frequency on the dispersion curve where the wave number is 0. Furthermore, the first passive structure is not electrically connected to the first electrode layer, and the second passive structure is not electrically connected to the second electrode layer; therefore, the first passive structure and the second passive structure have no electrical connection to Kt. 2 The impact is relatively small, thereby improving the performance of the filter device, including the bulk acoustic resonator, such as insertion loss and out-of-band suppression.

[0056] Furthermore, it also includes: a third dielectric portion in contact with the electrode layer; and a surrounding groove located within the third dielectric portion, inside the resonant region, inside the raised portion, and adjacent to the raised portion. By adding the surrounding groove inside the resonant region, a first segment region is formed by the surrounding groove, and a second segment region is formed by the raised portion. By setting the cutoff frequency of the first segment region to be greater than the cutoff frequency of the middle part of the resonant region inside the surrounding groove, and setting the cutoff frequency of the second segment region to be less than the cutoff frequency of the middle part, a piston mode is formed, suppressing higher-order parasitic modes of transverse acoustic waves and reducing the series resonant frequency (f). s Near and less than f s Partial noise.

[0057] In the method for forming the bulk acoustic resonator of the present invention, the first raised portion of the first passive structure is located inside the resonant region and overlaps with the first electrode layer. Similarly, the second raised portion of the second passive structure is located inside the resonant region and overlaps with the second electrode layer. This allows for matching the acoustic impedance of the resonant region with that of the evanescent region outside the resonant region, thereby allowing more sound waves generated in the resonant region to propagate into the evanescent region. Furthermore, the cutoff frequency of the evanescent region is matched (e.g., equal to or less than) the cutoff frequency of the resonant region, which attenuates the sound waves entering the evanescent region, suppresses parasitic edge modes, and enhances Z-axis propagation. p and the corresponding Q value. The cutoff frequency is the frequency at which the wave number on the dispersion curve is 0. Furthermore, the first passive structure is not electrically connected to the first electrode layer, and the second passive structure is not electrically connected to the second electrode layer; therefore, the first passive structure and the second passive structure have no electrical connection to Kt. 2 The impact is relatively small, thereby improving the performance of the filter device, including the bulk acoustic resonator, such as insertion loss and out-of-band suppression.

[0058] Furthermore, it also includes: forming a third dielectric portion in contact with the electrode layer; and forming a surrounding groove located within the third dielectric portion, inside the resonant region, inside the raised portion, and adjacent to the raised portion. By adding the surrounding groove inside the resonant region, a first segment region is formed by the surrounding groove, and a second segment region is formed by the raised portion. By setting the cutoff frequency of the first segment region to be greater than the cutoff frequency of the middle part of the resonant region inside the surrounding groove, and setting the cutoff frequency of the second segment region to be less than the cutoff frequency of the middle part, a piston mode is formed, suppressing higher-order parasitic modes of transverse acoustic waves and reducing the series resonant frequency (f). s (near and less than f) s Partial noise. Attached Figure Description

[0059] Figure 1 This is a schematic diagram of a bulk acoustic wave filter circuit.

[0060] Figure 2 This is a structural schematic diagram of an FBAR 200;

[0061] Figures 3 to 6 This is a schematic diagram of the structure of a bulk acoustic resonator 3000 according to an embodiment of the present invention;

[0062] Figure 7This is a schematic diagram of the structure of a hexagonal crystal system grain;

[0063] Figure 8 (i) is a schematic diagram of the structure of an orthorhombic crystal system grain;

[0064] Figure 8 (ii) is a schematic diagram of a tetragonal crystal grain structure;

[0065] Figure 8 (iii) is a schematic diagram of a cubic crystal system grain structure;

[0066] Figure 9 This is a schematic diagram of the acoustic dispersion curve 600 of a bulk acoustic resonator according to an embodiment of the present invention;

[0067] Figure 10 This is a schematic diagram of the parallel impedance curve 700 of a bulk acoustic resonator according to an embodiment of the present invention;

[0068] Figures 11 to 14 This is a schematic diagram of the structure of a bulk acoustic wave resonator 3000 according to an embodiment of the present invention, wherein, Figure 11 This is a schematic diagram of the first cross-section structure of the solid acoustic resonant device 3000 and a schematic diagram of the sound velocity distribution in the corresponding region.

[0069] Figure 15 This is a schematic diagram of the acoustic wave dispersion curve of a bulk acoustic resonator according to an embodiment of the present invention;

[0070] Figure 16 This is a schematic diagram of the first cross-sectional structure of a bulk acoustic resonant device 3000 according to another embodiment of the present invention and a schematic diagram of the sound velocity distribution in the corresponding region.

[0071] Figures 17-18 This is a schematic diagram of the structure of a bulk acoustic wave resonator 8000 according to an embodiment of the present invention;

[0072] Figure 19 This is a structural schematic diagram of a wireless communication device 900;

[0073] Figure 20 This is a schematic flowchart of a method for forming a bulk acoustic resonator device according to an embodiment of the present invention;

[0074] Figures 21 to 24 This is a cross-sectional structural schematic diagram of a method for forming a bulk acoustic resonator 1100 according to an embodiment of the present invention;

[0075] Figure 25 This is a cross-sectional structural schematic diagram of a method for forming a bulk acoustic resonant device 1100 according to another embodiment of the present invention, and a schematic diagram of the sound velocity distribution in the corresponding region.

[0076] Figure 26 and Figure 27 This is a cross-sectional structural schematic diagram (A) of a method for forming a bulk acoustic resonator 1100 according to another embodiment of the present invention, wherein... Figure 27 This is a schematic diagram of the first cross-section structure of the bulk acoustic resonant device 1100 and a schematic diagram of the sound velocity distribution in the corresponding region;

[0077] Figures 28 to 31 This is a cross-sectional structural schematic diagram of a method for forming a bulk acoustic resonator 1200 according to an embodiment of the present invention;

[0078] Figure 32 This is a schematic diagram comparing two series admittance curves. Detailed Implementation

[0079] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0080] Many specific details are set forth in the following description in order to provide a full understanding of the invention, but the invention may also be practiced in other ways different from those described herein, and therefore the invention is not limited to the specific embodiments disclosed below.

[0081] As described in the background section, the acoustic waves generated in the resonant region propagate along the side surfaces of the two electrode layers to the lateral edge of the piezoelectric layer, and excite parasitic edge modes at the edge, generating parasitic resonance, thereby reducing Z. p And the corresponding Q value.

[0082] The inventors of this invention discovered that the raised portion of the passive structure is located inside the resonant region and overlaps with the electrode layer. This allows for matching the acoustic impedance of the resonant region with that of the attenuation region outside the resonant region, thereby allowing more sound waves generated in the resonant region to propagate into the attenuation region. Furthermore, the cutoff frequency of the attenuation region matches (e.g., is equal to or less than) the cutoff frequency of the resonant region, which attenuates the sound waves entering the attenuation region, suppresses parasitic edge modes, and enhances Z-axis impedance. p and the corresponding Q value. Furthermore, the passive structure is not electrically connected to the electrode layer, therefore the passive structure has no effect on Kt. 2 The impact is relatively small.

[0083] To address the aforementioned problems, this invention provides a bulk acoustic wave resonator, comprising: a cavity; a first electrode layer, at least one end of which is located above or within the cavity; a piezoelectric layer, the piezoelectric layer including a first side and a second side perpendicular to the first side in a vertical direction, the cavity being located on the first side, the first electrode layer being located on the first side, and the first electrode layer contacting the piezoelectric layer; a second electrode layer located on the second side, contacting the piezoelectric layer, the overlapping region of the first electrode layer, the second electrode layer, and the piezoelectric layer being a resonant region; a first passive structure located on the first side, having a first overlapping portion with at least one edge of the first electrode layer; and a second passive structure located on the second side, having a second overlapping portion with at least one edge of the second electrode layer.

[0084] The first passive structure includes: a first raised portion located inside the resonant region, having a first overlapping portion with at least one edge of the first electrode layer, the first raised portion being used to match the acoustic impedance of the resonant region and at least one attenuation region outside the resonant region, allowing more sound waves generated in the resonant region to enter the at least one attenuation region; a first dielectric portion located between the first raised portion and the first electrode layer, used to electrically isolate the first electrode layer from the first passive structure; and a first extension portion located outside the resonant region and within the at least one attenuation region, used to attenuate sound waves entering the at least one attenuation region, the first raised portion protruding relative to the first extension portion.

[0085] The second passive structure includes: a second raised portion located inside the resonant region, having a second overlapping portion with at least one edge of the second electrode layer, the second raised portion being used to match the acoustic impedance of the resonant region and the at least one attenuation region, allowing more sound waves generated in the resonant region to enter the at least one attenuation region; a second dielectric portion located between the second raised portion and the second electrode layer, used to electrically isolate the second electrode layer and the second passive structure; and a second extension portion located outside the resonant region and within the at least one attenuation region, used to attenuate sound waves entering the at least one attenuation region, the second raised portion protruding relative to the second extension portion.

[0086] In some embodiments, the first passive structure and the second passive structure surround the resonant region.

[0087] In some embodiments, the thickness of the first passive structure is equal to or less than the thickness of the first electrode layer, and the thickness of the second passive structure is equal to or less than the thickness of the second electrode layer.

[0088] In some embodiments, the at least one attenuation region includes a first attenuation region, the first cutoff frequency of the first attenuation region being equal to or less than the cutoff frequency of the resonant region, and the first attenuation region corresponding to the overlapping region of the first extension, the piezoelectric layer, and the second extension.

[0089] In some embodiments, the bulk acoustic resonator further includes: a first electrode extension layer located on the first side and connected to the first electrode layer; and a second electrode extension layer located on the second side and connected to the second electrode layer.

[0090] In some embodiments, the at least one attenuation region includes a second attenuation region, the second cutoff frequency of the second attenuation region being equal to or less than the cutoff frequency of the resonant region, and the second attenuation region corresponding to the overlapping region of the second electrode extension layer, the piezoelectric layer and the first extension.

[0091] In some embodiments, the at least one attenuation region includes a third attenuation region, the third cutoff frequency of the third attenuation region being equal to or less than the cutoff frequency of the resonant region, and the third attenuation region corresponding to the overlapping region of the second extension, the piezoelectric layer and the first electrode extension layer.

[0092] In some embodiments, at least one edge of the first electrode layer is sloped down, corresponding to the first passive structure, and at least one edge of the second electrode layer is sloped down, corresponding to the second passive structure.

[0093] In some embodiments, the width of the first raised portion is an integer multiple of half the wavelength of the sound wave generated in the resonant region, and the width of the second raised portion is an integer multiple of half the wavelength of the sound wave generated in the resonant region.

[0094] In some embodiments, the thickness of the first extension is less than the thickness of the first electrode layer, and the thickness of the second extension is less than the thickness of the second electrode layer.

[0095] In some embodiments, the first extension includes a first sub-part and a second sub-part, the second sub-part and the piezoelectric layer being located on opposite sides of the first sub-part, and the material of the first sub-part being different from the material of the second sub-part.

[0096] In some embodiments, the second extension includes a third sub-part and a fourth sub-part, the piezoelectric layer and the fourth sub-part are located on opposite sides of the third sub-part, and the material of the third sub-part is different from that of the fourth sub-part.

[0097] In some embodiments, the first extension contacts the piezoelectric layer, and the second extension contacts the piezoelectric layer.

[0098] In some embodiments, the first dielectric portion is further located between the piezoelectric layer and the first extension portion, and the second dielectric portion is further located between the piezoelectric layer and the second extension portion.

[0099] In some embodiments, a first slot is included between the first extension and the piezoelectric layer, and a second slot is included between the piezoelectric layer and the second extension.

[0100] In some embodiments, it further includes: a third dielectric portion located on the second side and in contact with the second electrode layer; and a surrounding groove located within the third dielectric portion, inside the resonant region, inside the second raised portion, and adjacent to the second raised portion.

[0101] In some embodiments, the shape of the circumferential groove includes: a circle, an ellipse, or a polygon.

[0102] In some embodiments, the device further includes: a third dielectric portion located on the first side and in contact with the first electrode layer; and a surrounding groove located within the third dielectric portion, inside the resonant region, inside the first raised portion, and adjacent to the first raised portion.

[0103] In some embodiments, the shape of the circumferential groove includes: a circle, an ellipse, or a polygon.

[0104] It should be noted that the first raised portion of the first passive structure is located inside the resonant region and overlaps with the first electrode layer, and the second raised portion of the second passive structure is located inside the resonant region and overlaps with the second electrode layer. This allows for matching the acoustic impedance of the resonant region with that of the evanescent region outside the resonant region, thereby allowing more sound waves generated in the resonant region to propagate into the evanescent region. Furthermore, the cutoff frequency of the evanescent region matches (e.g., is equal to or less than) the cutoff frequency of the resonant region, which can attenuate the sound waves entering the evanescent region, suppress parasitic edge modes, and improve Z-axis impedance. p and the corresponding Q value. The cutoff frequency is the frequency on the dispersion curve where the wave number is 0. Furthermore, the first passive structure is not electrically connected to the first electrode layer, and the second passive structure is not electrically connected to the second electrode layer; therefore, the first passive structure and the second passive structure have no electrical connection to Kt. 2 The impact is relatively small, thereby improving the performance of the filter device, including the bulk acoustic resonator, such as insertion loss and out-of-band suppression.

[0105] Figures 3 to 6A specific embodiment of the bulk acoustic resonator device of the present invention is shown, but the present invention can also be implemented in other ways different from those described herein, and therefore the present invention is not limited to the specific embodiments disclosed below. Figure 3 This is a schematic diagram of the first cross-sectional structure of the bulk acoustic resonator. Figure 4 This is a schematic diagram of the second cross-sectional structure of the bulk acoustic resonator. Figure 5 This is a schematic diagram of the first top view of the first electrode layer of the bulk acoustic resonator relative to the first cross-section. Figure 6 This is a schematic diagram of the second top view of the second electrode layer of the bulk acoustic resonator relative to the first cross-section.

[0106] Figure 3 This is a cross-sectional structural diagram of a bulk acoustic resonator 3000 according to an embodiment of the present invention.

[0107] like Figure 3As shown, the bulk acoustic wave resonator 3000 includes: a piezoelectric layer 3001, the piezoelectric layer 3001 including a first side 3002 and a second side 3003 opposite to the first side 3002 in the vertical direction; a first electrode layer 3004, located on the first side 3002 and in contact with the piezoelectric layer 3001, the first electrode layer 3004 including a first edge and a second edge opposite to the first edge in the horizontal direction, the first edge being sloping downwards; a first electrode extension layer 3005, located on the first side 3002 and in contact with the piezoelectric layer 3001, and connected to the second edge; a second electrode layer 3006, located on the second side 3003 and in contact with the piezoelectric layer 3001, the second electrode layer 3006 including a third edge and a fourth edge opposite to the third edge in the horizontal direction, the fourth edge being sloping downwards; The second electrode extension layer 3007 is located on the second side 3003, contacts the piezoelectric layer 3001, and is connected to the third edge; the overlapping area of ​​the first electrode layer 3004, the second electrode layer 3006, and the piezoelectric layer 3001 is the resonant region 3100, wherein the first edge corresponds to the third edge in the vertical direction, and the second edge corresponds to the fourth edge in the vertical direction; the first electrode extension layer 3005 and the second electrode extension layer 3007 are located outside the resonant region 3100 and have no overlapping portion; the first passivation layer 3008 is located on the first side 3002, the first passivation layer 3008 located inside the resonant region 3100 covers the first electrode layer 3004, and the first passivation layer 3008 located outside the resonant region 3100... The piezoelectric layer 3001 covering the outer side of the first edge and the first electrode extension layer 3005 covering the outer side of the second edge; the second passivation layer 3009, located on the second side 3003, the second passivation layer 3009 located inside the resonant region 3100 covering the second electrode layer 3006, the second passivation layer 3009 located outside the resonant region 3100 covering the second electrode extension layer 3007 covering the outer side of the third edge and the piezoelectric layer 3001 covering the outer side of the fourth edge;The first edge layer 3010 is located on the first side 3002 and contacts the first passivation layer 3008. The first edge layer 3010 includes a first raised portion (unmarked) and a first extended portion (unmarked). The first raised portion protrudes relative to the first extended portion. The first raised portion is located inside the resonant region 3100 and overlaps with the first electrode layer 3004 on the first edge side. The first raised portion and the first electrode layer 3004 are located on opposite sides of the first passivation layer 3008. The first extended portion is located in the resonant region 3100. The outer side, located outside the first edge, has no overlap with the first electrode layer 3004. The first extension and the piezoelectric layer 3001 are located on both sides of the first passivation layer 3008 in the vertical direction. The second overlap layer 3011 is located on the second side 3003, contacting the second passivation layer 3009. The second overlap layer 3011 includes a second raised portion (unmarked) and a second extension portion (unmarked). The second raised portion protrudes relative to the second extension portion. The second raised portion is located inside the resonant region 3100 and has an overlap with the second electrode layer 3006 on the fourth edge side. The second raised portion and the second electrode layer 3006 are located on both sides of the second passivation layer 3009. The second extension portion is located outside the resonant region 3100, outside the fourth edge, and has no overlap with the second electrode layer 3006. The second extension portion and the piezoelectric layer 3001 are located on both sides of the second passivation layer 3009 in the vertical direction.

[0108] In this embodiment, the material of the piezoelectric layer 3001 includes, but is not limited to, one of the following: aluminum nitride, aluminum nitride alloy, gallium nitride, zinc oxide, lithium tantalate, lithium niobate, lead zirconate titanate (PZT), lead magnesium niobate-lead titanate.

[0109] In this embodiment, the piezoelectric layer 3001 is a flat layer, and the piezoelectric layer 3001 includes multiple grains, including a first grain and a second grain, wherein the first grain and the second grain are any two grains among the multiple grains. Those skilled in the art know that the crystal orientation, crystal plane, etc., of grains can be represented based on a coordinate system. For example... Figure 7 As shown, hexagonal grains, such as aluminum nitride grains, are represented using an ac-3D coordinate system (including the a-axis and c-axis). Figure 8 As shown, for grains of (i) orthorhombic crystal system (a≠b≠c), (ii) tetragonal crystal system (a=b≠c), and (iii) cubic crystal system (a=b=c), an xyz three-dimensional coordinate system (including the x-axis, y-axis, and z-axis) is used. Besides the two examples above, grains can also be represented based on other coordinate systems known to those skilled in the art; therefore, this invention is not limited to the two examples described above.

[0110] In this embodiment, the first grain can be represented based on a first three-dimensional coordinate system, and the second grain can be represented based on a second three-dimensional coordinate system. The first three-dimensional coordinate system includes at least a first coordinate axis along a first direction and a third coordinate axis along a third direction, and the second three-dimensional coordinate system includes at least a second coordinate axis along a second direction and a fourth coordinate axis along a fourth direction. The first coordinate axis corresponds to the height of the first grain, and the second coordinate axis corresponds to the height of the second grain.

[0111] In this embodiment, the first direction and the second direction are the same or opposite. It should be noted that the first direction and the second direction being the same means that the angle between the vector along the first direction and the vector along the second direction ranges from 0 degrees to 5 degrees; the first direction and the second direction being opposite means that the angle between the vector along the first direction and the vector along the second direction ranges from 175 degrees to 180 degrees.

[0112] In another embodiment, the first solid coordinate system is an ac solid coordinate system, wherein the first coordinate axis is a first c-axis and the third coordinate axis is a first a-axis; the second solid coordinate system is an ac solid coordinate system, wherein the second coordinate axis is a second c-axis and the fourth coordinate axis is a second a-axis, wherein the first c-axis and the second c-axis point in the same or opposite directions.

[0113] In another embodiment, the first solid coordinate system further includes a fifth coordinate axis along a fifth direction, and the second solid coordinate system further includes a sixth coordinate axis along a sixth direction. In another embodiment, the first direction and the second direction are the same or opposite, and the third direction and the fourth direction are the same or opposite. It should be noted that the third direction and the fourth direction being the same means that the angle between the vector along the third direction and the vector along the fourth direction ranges from 0 degrees to 5 degrees; the third direction and the fourth direction being opposite means that the angle between the vector along the third direction and the vector along the fourth direction ranges from 175 degrees to 180 degrees.

[0114] In another embodiment, the first solid coordinate system is an xyz solid coordinate system, wherein the first coordinate axis is the first z-axis, the third coordinate axis is the first y-axis, and the fifth coordinate axis is the first x-axis; the second solid coordinate system is an xyz solid coordinate system, wherein the second coordinate axis is the second z-axis, the fourth coordinate axis is the second y-axis, and the sixth coordinate axis is the second x-axis. In another embodiment, the first z-axis and the second z-axis point in the same direction, and the first y-axis and the second y-axis point in the same direction. In another embodiment, the first z-axis and the second z-axis point in opposite directions, and the first y-axis and the second y-axis point in opposite directions. In another embodiment, the first z-axis and the second z-axis point in the same direction, and the first y-axis and the second y-axis point in opposite directions. In another embodiment, the first z-axis and the second z-axis point in opposite directions, and the first y-axis and the second y-axis point in the same direction.

[0115] In this embodiment, the piezoelectric layer 3001 comprises multiple grains, and the rocking curve of the crystal formed by these multiple grains has a half-width at half-maximum (FWHM) of less than 2.5 degrees. It should be noted that the rocking curve describes the angular divergence of a specific crystal plane (a crystal plane determined by the diffraction angle) in the sample, represented by a planar coordinate system. The horizontal axis represents the angle between the crystal plane and the sample plane, and the vertical axis represents the diffraction intensity of the crystal plane at a given angle. The rocking curve is used to represent crystal quality; a smaller FWHM angle indicates better crystal quality. Furthermore, the full width at half-maximum (FWHM) refers to the distance between two points within a peak of a function whose corresponding function values ​​are equal to half the peak value.

[0116] In this embodiment, the material of the first electrode layer 3004 includes, but is not limited to, at least one of the following: molybdenum, ruthenium, tungsten, platinum, iridium, aluminum, and beryllium. The material of the first electrode extension layer 3005 includes, but is not limited to, at least one of the following: molybdenum, ruthenium, tungsten, platinum, iridium, aluminum, beryllium, copper, and gold. In this embodiment, the material of the first electrode layer 3004 is the same as the material of the first electrode extension layer 3005.

[0117] In this embodiment, the material of the second electrode layer 3006 includes, but is not limited to, at least one of the following: molybdenum, ruthenium, tungsten, platinum, iridium, aluminum, and beryllium. The material of the second electrode extension layer 3007 includes, but is not limited to, at least one of the following: molybdenum, ruthenium, tungsten, platinum, iridium, aluminum, beryllium, copper, and gold. In this embodiment, the material of the second electrode layer 3006 is the same as the material of the second electrode extension layer 3007.

[0118] In another embodiment, the material of the electrode layer may be different from the material of the electrode extension layer.

[0119] In this embodiment, the material of the first passivation layer 3008 includes, but is not limited to, one of the following: silicon dioxide, silicon oxynitride, silicon oxycarbide, silicon nitride, titanium oxide, aluminum oxide, hafnium silicate, zirconium silicate, hafnium dioxide, and zirconium dioxide. In this embodiment, the material of the second passivation layer 3009 includes, but is not limited to, one of the following: silicon dioxide, silicon oxynitride, silicon oxycarbide, silicon nitride, titanium oxide, aluminum oxide, hafnium silicate, zirconium silicate, hafnium dioxide, and zirconium dioxide. In this embodiment, the material of the first passivation layer 3008 is the same as the material of the second passivation layer 3009. In another embodiment, the materials of the first passivation layer (e.g., the first passivation layer 3008) and the second passivation layer (e.g., the second passivation layer 3009) may be different.

[0120] In this embodiment, the material of the first overlap layer 3010 includes, but is not limited to, at least one of the following: molybdenum, ruthenium, tungsten, platinum, iridium, aluminum, and beryllium. In this embodiment, the material of the first overlap layer 3010 is the same as the material of the electrode 3004.

[0121] In this embodiment, the material of the second edge layer 3011 includes, but is not limited to, at least one of the following: molybdenum, ruthenium, tungsten, platinum, iridium, aluminum, and beryllium. In this embodiment, the material of the second edge layer 3011 is the same as the material of the electrode 3006.

[0122] In another embodiment, the material of the edge layer may be different from that of the electrode layer. For example, the material of the edge layer may be tungsten or platinum, and the material of the electrode layer may be molybdenum.

[0123] In another embodiment, the overlap layer includes a first overlap sub-layer and a second overlap sub-layer, the first overlap sub-layer contacting the passivation layer, the second overlap sub-layer contacting the first overlap layer, the second overlap sub-layer and the passivation layer being located on opposite sides of the first overlap layer, the material of the first overlap sub-layer being different from the material of the second overlap layer, for example, the material of the first overlap layer being molybdenum, and the material of the second overlap layer being platinum or tungsten.

[0124] In this embodiment, the bulk acoustic wave resonator 3000 further includes: a first passive structure 3012 located on the first side 3002, contacting the first edge of the first electrode layer 3004 and the piezoelectric layer 3001 outside the first edge, the first passive structure 3012 including the first overlap layer 3010 and a first dielectric portion (not labeled) on the first passivation layer 3008 that overlaps with the first overlap layer 3010; and a second passive structure 3013 located on the second side 3003, contacting the fourth edge of the second electrode layer 3006 and the piezoelectric layer 3001 outside the fourth edge, the second passive structure 3013 including the second overlap layer 3011 and a second dielectric portion (not labeled) on the second passivation layer 3009 that overlaps with the second overlap layer 3011. It should be noted that the dielectric portion can electrically isolate the electrode layer and the edge layer, making them non-conductive. Thus, the edge layer is passive, and the combined structure of the dielectric portion and the edge layer is also passive.

[0125] In this embodiment, the first thickness of the first passive structure 3012 is less than the thickness of the first electrode layer 3004, the second thickness of the second passive structure 3013 is less than the thickness of the second electrode layer 3006, and the first thickness is equal to or approximately equal to the second thickness.

[0126] In this embodiment, the first width of the first raised portion matches the transverse acoustic wave main mode generated by the resonant region 3100, for example, Rayleigh Lamb S1 mode (1 st order Symmetrical mode), or TE1 mode (1 st The first width is equal to or approximately equal to the second width of the transverse acoustic wave main mode generated by the resonant region 3100 (e.g., the second width is an integer multiple of half the wavelength). It should be noted that the first and second raised portions are used to match the acoustic impedance of the resonant region and the attenuation region, thereby allowing more acoustic waves generated in the resonant region to propagate into the attenuation region.

[0127] In this embodiment, the third thickness of the first extension is less than the thickness of the first electrode layer 3004, the fourth thickness of the second extension is less than the thickness of the second electrode layer 3006, and the third thickness is equal to or approximately equal to the fourth thickness.

[0128] In this embodiment, the overlapping area of ​​the first extension, the second electrode extension layer 3007, and the piezoelectric layer 3001 is the attenuation region 3200; the overlapping area of ​​the second extension, the first electrode extension layer 3005, and the piezoelectric layer 3001 is the attenuation region 3300; the first cutoff frequency of the attenuation region 3200 matches (for example, is equal to or less than) the cutoff frequency of the resonant region 3100, the second cutoff frequency of the attenuation region 3300 matches (for example, is equal to or less than) the cutoff frequency of the resonant region 3100, and the first cutoff frequency is equal to or approximately equal to the second cutoff frequency.

[0129] It should be noted that matching (e.g., being equal to or less than) the cutoff frequency of the attenuation region to the cutoff frequency of the resonant region allows the sound wave entering the attenuation region to exhibit an evanescent mode, meaning that the wavenumber within the attenuation region contains only the imaginary part, resulting in exponential attenuation of the sound wave. For a clearer illustration of the beneficial effects of the embodiments of the present invention, see [link to relevant documentation]. Figure 9 Two exemplary Type II acoustic wave dispersion curves 600 are shown. The horizontal axis of the dispersion curve coordinate system represents the wavenumber, the vertical axis represents the frequency, the origin of the coordinate system represents a wavenumber of 0, the left side of the origin represents a wavenumber containing only the imaginary part, and the right side of the origin represents a wavenumber containing only the real part. For example... Figure 9 As shown, the first dispersion curve 601 represents the dispersion relationship in the resonant region, and the intersection of the first dispersion curve 601 and the vertical axis represents the first cutoff frequency 602 of the resonant region; the second dispersion curve 603 represents the dispersion relationship in the attenuation region, and the intersection of the second dispersion curve 603 and the vertical axis represents the second cutoff frequency 604 of the attenuation region, where the second cutoff frequency 604 is less than the first cutoff frequency 602. See also... Figure 9 For the parallel resonant frequency f p The wavenumber of the first dispersion curve 601 contains only the real part, and the wavenumber of the second dispersion curve 603 contains only the imaginary part. Therefore, after the sound wave propagates from the resonant region into the attenuation region, it exhibits an attenuation mode, resulting in exponential attenuation. Specifically, the expression for the sound wave displacement includes exp(-jkx), where the wavenumber k contains only the imaginary part. It should be noted that the Type I sound wave dispersion curve also exhibits similar dispersion characteristics.

[0130] Figure 10 Two parallel impedance curves are shown, where the horizontal axis represents frequency and the vertical axis represents the relative parallel impedance value. The relative parallel impedance value is the ratio of the absolute parallel impedance value to a specific parallel impedance value. For example, if the absolute parallel impedance value is 300 ohms and the specific parallel impedance value is 500 ohms, then the relative parallel impedance value is 0.6(300 / 500). See also Figure 10The first parallel impedance curve 701 represents the relative parallel impedance curve of the bulk acoustic wave resonator excluding the passive structure, and the second parallel impedance curve 703 represents the relative parallel impedance curve of the bulk acoustic wave resonator including the passive structure. For example... Figure 10 As shown, for the parallel resonant frequency f p The value corresponding to the second parallel impedance curve 703 is greater than the value corresponding to the first parallel impedance curve 701. It should be noted that the passive structure can attenuate the laterally propagating sound waves generated in the resonant region, suppress parasitic edge modes, and improve Z-axis impedance. p and the corresponding Q value. Furthermore, the passive structure has no electrical connection to the electrode layer, therefore the passive structure is related to Kt. 2 The impact is relatively small.

[0131] In this embodiment, the bulk acoustic resonator 3000 further includes: a cavity 3014, the first electrode layer 3004 located within the cavity 3014, one end of the first electrode extension layer 3005 located within the cavity 3014, and the first passive structure 3012 located within the cavity 3014. In another embodiment, the lower electrode layer (e.g., the first electrode layer 3004) may be located above the cavity, covering the cavity; the passive structure corresponding to the lower electrode layer is located outside the cavity.

[0132] Figure 4 This is a cross-sectional structural diagram (B) of a bulk acoustic resonator 3000 according to an embodiment of the present invention.

[0133] like Figure 4As shown, the bulk acoustic wave resonator 3000 includes: a piezoelectric layer 3001, which includes a first side 3002 and a second side 3003; a first electrode layer 3004, located on the first side 3002 and in contact with the piezoelectric layer 3001, the first electrode layer 3004 further including a fifth edge and a sixth edge opposite to the fifth edge in the horizontal direction, the fifth edge being downsloping and the sixth edge being downsloping; and a second electrode layer 3006, located on the second side 3003 and in contact with the piezoelectric layer 3001, the second electrode layer 3006 further including a seventh edge. The seventh edge and the eighth edge, which are opposite each other in the horizontal direction, are both sloped downwards. Within the resonant region 3100, the fifth edge corresponds vertically to the seventh edge, and the sixth edge corresponds vertically to the eighth edge. The first passivation layer 3008, located on the first side 3002, covers the first electrode layer 3004 inside the resonant region 3100. The first passivation layer 3008 outside the resonant region 3100 also covers the piezoelectric layer 3001 outside the fifth edge and the sixth edge. The piezoelectric layer 3001 on the outer edge; the second passivation layer 3009, located on the second side 3003, the second passivation layer 3009 located inside the resonant region 3100 covers the second electrode layer 3006, the second passivation layer 3009 located outside the resonant region 3100 also covers the piezoelectric layer 3001 on the outer edge of the seventh edge and the piezoelectric layer 3001 on the outer edge of the eighth edge; the first overlap layer 3010, located on the first side 3002, contacts the first passivation layer 3008, the first overlap layer 3010 includes the first raised portion and the first extended portion. The first raised portion protrudes relative to the first extended portion. The first raised portion is located inside the resonant region 3100 and overlaps with the first electrode layer 3004 on the fifth edge side and the sixth edge side. The first raised portion and the first electrode layer 3004 are located on both sides of the first passivation layer 3008. The first extended portion is located outside the resonant region 3100 and also outside the fifth edge and the sixth edge, without overlapping with the first electrode layer 3004. The first extended portion and the piezoelectric layer 3001 are located on both sides of the first passivation layer 3008 in the vertical direction.The second overlap layer 3011, located on the second side 3003, contacts the second passivation layer 3009. The second overlap layer 3011 includes a second raised portion and a second extended portion. The second raised portion protrudes relative to the second extended portion. The second raised portion is located inside the resonant region 3100 and overlaps with the second electrode layer 3006 on the seventh and eighth edge sides. The second raised portion and the second electrode layer 3006 are located on both sides of the second passivation layer 3009. The second extended portion is located outside the resonant region 3100 and also outside the seventh and eighth edges, without overlap with the second electrode layer 3006. The second extended portion and the piezoelectric layer 3001 are located on both sides of the second passivation layer 3009 in the vertical direction.

[0134] In this embodiment, the region where the first extension, the second extension, and the piezoelectric layer 3001 overlap is the attenuation region 3400; the third cutoff frequency of the attenuation region 3400 matches (for example, is equal to or less than) the cutoff frequency of the resonant region 3100.

[0135] Figure 5 This is a schematic diagram of the first top view of a bulk acoustic resonator 3000 based on the first electrode layer 3004 relative to the cross section A, according to an embodiment of the present invention.

[0136] like Figure 5 As shown, the bulk acoustic wave resonator 3000 includes: a first electrode layer 3004 (shown as dashed lines), the first electrode layer 3004 being hexagonal, including a first edge, a second edge, a fifth edge, a sixth edge, a ninth edge, and a tenth edge; a first electrode extension layer 3005, connected to the second edge; a first overlap layer 3010, having overlapping portions with multiple edge sides of the first electrode layer 3004, adjacent to the first electrode extension layer 3005, the first overlap layer 3010 including a first raised portion 3015 and a first extension portion 3016; wherein, the first raised portion 3015 is located inside the edge of the first electrode layer 3004, having overlapping portions with the fifth edge side, the ninth edge side, the first edge side, the sixth edge side, and the tenth edge side; wherein, the first extension portion 3016 is located outside the fifth edge, the ninth edge, the first edge, the sixth edge, and the tenth edge, and has no overlapping portion with the first electrode layer 3004.

[0137] In this embodiment, the width w of the first overlap layer 3010 is the same for each edge, and correspondingly, the width of the first raised portion 3015 is the same for each edge, and the width of the first extension portion 3016 is the same for each edge.

[0138] In this embodiment, the first passive structure 3012 includes a first overlap layer 3010, which is adjacent to the first electrode extension layer 3005. In this embodiment, the first passive structure 3012 includes a first raised portion 3015, which overlaps with the fifth edge side, the ninth edge side, the first edge side, the sixth edge side, and the tenth edge side. In this embodiment, the first passive structure 3012 further includes a first extension portion 3016, located outside the fifth edge, the ninth edge, the first edge, the sixth edge, and the tenth edge, and does not overlap with the first electrode layer 3004.

[0139] In this embodiment, the width w of each edge of the first passive structure 3012 is the same.

[0140] Figure 6 This is a schematic diagram of the second top view of a bulk acoustic resonator 3000 based on the second electrode layer 3006 relative to the cross section A, according to an embodiment of the present invention.

[0141] like Figure 6 As shown, the bulk acoustic resonator 3000 includes: a second electrode layer 3006 (shown as dashed lines), which is hexagonal and includes the third edge, the fourth edge, the seventh edge, the eighth edge, the eleventh edge, and the twelfth edge; a second electrode extension layer 3007 connected to the third edge; and a second overlap layer 3011 having overlapping portions with multiple edge sides of the second electrode layer 3006 and adjacent to the second electrode extension layer 3007. The second overlap layer 3011 includes a second raised portion 3017 and a second extension portion 3018. The second raised portion 3017 is located inside the edge of the second electrode layer 3006 and has overlapping portions with the seventh edge side, the eleventh edge side, the fourth edge side, the eighth edge side, and the twelfth edge side. The second extension portion 3018 is located outside the seventh edge, the eleventh edge, the fourth edge, the eighth edge, and the twelfth edge and has no overlapping portion with the second electrode layer 3006.

[0142] In this embodiment, the width w of the second overlap layer 3011 is the same for each edge, and correspondingly, the width of the second raised portion 3017 is the same for each edge, and the width of the second extension portion 3018 is the same for each edge.

[0143] In this embodiment, the second passive structure 3013 includes a second overlap layer 3011, adjacent to the second electrode extension layer 3007. In this embodiment, the second passive structure 3013 includes a second raised portion 3017, overlapping with the seventh edge side, the eleventh edge side, the fourth edge side, the eighth edge side, and the twelfth edge side. In this embodiment, the second passive structure 3013 further includes a second extension portion 3018, located outside the seventh edge, the eleventh edge, the fourth edge, the eighth edge, and the twelfth edge, without overlapping with the second electrode layer 3006.

[0144] In this embodiment, the width w of each edge of the second passive structure 3013 is the same.

[0145] In this embodiment, the first passive structure 3012 and the second passive structure 3013 surround the first electrode layer 3004 and the second electrode layer 3006, that is, surround the resonant region 3100.

[0146] It should be noted that the hexagonal shape of the electrode layer in the top view of this embodiment is a specific embodiment. Therefore, this invention is not limited to the disclosed specific embodiment. The top view of the electrode layer can also be other polygons (e.g., pentagons, heptagons), ellipses, etc.

[0147] In another embodiment, the bulk acoustic resonator includes a plurality of electrode extension layers, each connected to a plurality of edges of the electrode layers. A passive structure corresponding to the electrode layers is adjacent to the plurality of electrode extension layers and has a passive overlap portion with other edges besides the plurality of edges. The passive structure also includes a passive extension portion located outside the other edges.

[0148] In another embodiment, the bulk acoustic resonator includes three or more passive structures surrounding the resonant region of the bulk acoustic resonator.

[0149] Figures 11 to 14 A specific embodiment of the bulk acoustic resonator device of the present invention is shown, but the present invention can also be implemented in other ways different from those described herein, and therefore the present invention is not limited to the specific embodiments disclosed below. Figure 11 This is a schematic diagram of the first cross-section structure of the bulk acoustic resonator and a schematic diagram of the sound velocity distribution in the corresponding region. Figure 12 This is a schematic diagram of the second cross-sectional structure of the bulk acoustic resonator. Figure 13 This is a schematic diagram of the first top view of the first electrode layer of the bulk acoustic resonator relative to the first cross-section. Figure 14This is a schematic diagram of the second top view of the second electrode layer of the bulk acoustic resonator relative to the first cross-section.

[0150] This embodiment is a cross-sectional structure A of the bulk acoustic resonator 3000 in the above embodiment. Figure 3 Building upon the previous embodiment, the bulk acoustic wave resonator 3000 will continue to be described. The difference between this embodiment and the previous one is that the bulk acoustic wave resonator 3000 further includes a third dielectric section and a surrounding groove located within the third dielectric section. The following will provide a detailed description in conjunction with the accompanying drawings.

[0151] like Figures 11 to 14 As shown, the bulk acoustic resonator 3000 further includes: a third dielectric portion (not shown), located on the second side 3003 and in contact with the second electrode layer 3006; and a surrounding groove 3019, located within the third dielectric portion, inside the resonant region 3100, inside the second raised portion, and adjacent to the second raised portion.

[0152] In this embodiment, the circumferential groove 3019 is polygonal. In other embodiments, the circumferential groove may also be circular or elliptical.

[0153] It should be noted that the second passivation layer 3009 includes the third dielectric portion and the second dielectric portion.

[0154] In this embodiment, by adding the surrounding groove 3019 inside the resonant region 3100, a first region I formed by the surrounding groove 3019 and a second region II formed by the first raised portion 3015 and the second raised portion 3017 are created. By setting the cutoff frequency of the first region I to be greater than the cutoff frequency of the middle part (unmarked) of the resonant region 3100 inside the surrounding groove 3019, and setting the cutoff frequency of the second region II to be less than the cutoff frequency of the middle part, a piston mode is formed. See [link to documentation]. Figure 11 The diagram shows the sound velocity distribution under piston mode. The sound velocity is proportional to the cutoff frequency. Exciting the piston mode can suppress higher-order parasitic modes of transverse sound waves, such as... Figure 32 As shown, reducing the series resonant frequency (f s (near and less than f) s Partial noise.

[0155] To more clearly illustrate the beneficial effects of the embodiments of the present invention, see [link to relevant documentation]. Figure 15 Three exemplary Type II acoustic dispersion curves are shown. Figure 15(Curves 1, 2, and 3 in the diagram). In the dispersion curve coordinate system, the horizontal axis represents the wavenumber, the vertical axis represents the frequency, the origin of the coordinate system indicates a wavenumber of 0, the left side of the origin indicates the wavenumber contains only the imaginary part, and the right side of the origin indicates the wavenumber contains only the real part. For example... Figure 15 As shown, the first dispersion curve ( Figure 15 Curve 1) in the diagram represents the dispersion relation in the middle of the resonant region, and the intersection of the first dispersion curve with the vertical axis represents the first cutoff frequency of the resonant region. Figure 15 a) in the middle; the second dispersion curve ( Figure 15 Curve 2) represents the dispersion relationship of the first region I, and the intersection of the second dispersion curve with the vertical axis represents the second cutoff frequency of the first region I. Figure 15 In section b), the second cutoff frequency is greater than the first cutoff frequency; the third dispersion curve (curve 3 in Figure 15) represents the dispersion relationship of the second region II, and the intersection of the third dispersion curve with the vertical axis represents the third cutoff frequency of the second region II. Figure 15 In c), the third cutoff frequency is less than the first cutoff frequency. See also... Figure 15 For series resonant frequency ( Figure 15 The straight line f in s The first dispersion curve has a wavenumber of 0, exhibiting a resonant mode. The second dispersion curve has a wavenumber that contains only the real part, thus the higher-order parasitic modes of the transverse sound wave form a standing wave in the first region I, which can facilitate the propagation of the sound wave between the resonant region and the second region II. The third dispersion curve has a wavenumber that contains only the imaginary part, thus the higher-order parasitic modes of the transverse sound wave exhibit a decaying mode after propagating from the first region I into the second region II. Specifically, the expression for the transverse sound wave displacement includes exp(-jkx), where the wavenumber k contains only the imaginary part.

[0156] Figure 32 Two series admittance curves are shown, where the horizontal axis represents frequency and the vertical axis represents the relative series admittance value. The relative series admittance value is the ratio of the absolute series admittance value to a specific series admittance value. For example, if the absolute series admittance value is 1 Siemens and the specific series admittance value is 2 Siemens, then the relative series admittance value is 0.5 (1 / 2). See also Figure 32 First series admittance curve ( Figure 32 Curve 1) represents the relative series admittance curve of the bulk acoustic resonator excluding the surrounding groove 3019 and the passive structure, and the second series admittance curve ( Figure 32 Curve 2) in the figure represents the relative series admittance curve of the bulk acoustic resonator including the surrounding groove 3019 and the passive structure. Figure 32 As shown, for the series resonant frequency f sNearby and less than f s In the second series admittance curve, the corresponding ripple is smaller than the corresponding ripple on the first series admittance curve. It should be noted that the surrounding groove 3019 and the passive structure can form a piston mode in the resonant region 3100, suppressing higher-order parasitic modes of transverse acoustic waves, improving resonator performance, and reducing the series resonant frequency f. s Nearby and less than f s Partial noise.

[0157] Figure 16 A specific embodiment of the bulk acoustic resonator device of the present invention is shown, but the present invention can also be implemented in other ways different from those described herein, and therefore the present invention is not limited to the specific embodiments disclosed below. Figure 16 This is a schematic diagram of the first cross-sectional structure of the bulk acoustic resonator and a schematic diagram of the sound velocity distribution in the corresponding region.

[0158] This embodiment is a cross-sectional structure A of the bulk acoustic resonator 3000 in the above embodiment. Figure 3 Building upon the previous embodiment, the bulk acoustic wave resonator 3000 will continue to be described. The difference between this embodiment and the previous one is that the bulk acoustic wave resonator 3000 further includes a third dielectric section and a surrounding groove located within the third dielectric section. The following will provide a detailed description in conjunction with the accompanying drawings.

[0159] like Figure 16 As shown, the bulk acoustic resonator 3000 further includes: a third dielectric portion (not shown), located on the first side 3002 and in contact with the first electrode layer 3004; and a surrounding groove 3019, located within the third dielectric portion, inside the resonant region 3100, inside the first raised portion, and adjacent to the first raised portion.

[0160] In this embodiment, the circumferential groove 3019 is polygonal. In other embodiments, the circumferential groove may also be circular or elliptical.

[0161] It should be noted that the first passivation layer 3008 includes the third dielectric portion and the first dielectric portion.

[0162] In this embodiment, by adding the surrounding groove 3019 inside the resonant region 3100, a first region I formed by the surrounding groove 3019 and a second region II formed by the first raised portion 3015 and the second raised portion 3017 are created. By setting the cutoff frequency of the first region I to be greater than the cutoff frequency of the middle part (unmarked) of the resonant region 3100 inside the surrounding groove 3019, and setting the cutoff frequency of the second region II to be less than the cutoff frequency of the middle part, a piston mode is formed. See [link to documentation]. Figure 16 The diagram shows the sound velocity distribution under piston mode. The sound velocity is proportional to the cutoff frequency. Exciting the piston mode can suppress higher-order parasitic modes of transverse sound waves, such as... Figure 32 As shown, reducing the series resonant frequency (f s (near and less than f) s Partial noise.

[0163] Figure 17 and Figure 18 A specific embodiment of the bulk acoustic resonator device of the present invention is shown, but the present invention can also be implemented in other ways different from those described herein, and therefore the present invention is not limited to the specific embodiments disclosed below. Figure 17 This is a schematic diagram of the first cross-sectional structure of the bulk acoustic resonator. Figure 18 This is a schematic diagram of the second cross-sectional structure of the bulk acoustic resonator.

[0164] Figure 17 This is a cross-sectional structural diagram of a bulk acoustic resonator 8000 according to an embodiment of the present invention.

[0165] like Figure 17As shown, the bulk acoustic wave resonator 8000 includes: a piezoelectric layer 8001, the piezoelectric layer 8001 including a first side 8002 and a second side 8003 opposite to the first side 8002 in a vertical direction; a first electrode layer 8004, located on the first side 8002 and in contact with the piezoelectric layer 8001, the first electrode layer 8004 including a first edge and a second edge opposite to the first edge in a horizontal direction, the first edge being sloping downwards; a first electrode extension layer 8005, located on the first side 8002, in contact with the piezoelectric layer 8001, and connected to the second edge; and a second electrode layer 8006, located on the second side 8003 and in contact with the piezoelectric layer 8001. The second electrode layer 8006 includes a third edge and a fourth edge opposite to the third edge in the horizontal direction, the fourth edge being sloping downwards; the second electrode extension layer 8007 is located on the second side 8003, contacts the piezoelectric layer 8001, and is connected to the third edge; the overlapping area of ​​the first electrode layer 8004, the second electrode layer 8006, and the piezoelectric layer 8001 is the resonant region 8100, wherein the first edge corresponds to the third edge in the vertical direction, and the second edge corresponds to the fourth edge in the vertical direction; the first electrode extension layer 8005 and the second electrode extension layer 8007 are located outside the resonant region 8100 and have no overlapping portion; the first passivation layer... 8008, located on the first side 8002, the first passivation layer 8008 located inside the resonant region 8100 covers the first electrode layer 8004, and the first passivation layer 8008 located outside the resonant region 8100 covers the first electrode extension layer 8005 outside the second edge; the second passivation layer 8009, located on the second side 8003, the second passivation layer 8009 located inside the resonant region 8100 covers the second electrode layer 8006, and the second passivation layer 8009 located outside the resonant region 8100 covers the second electrode extension layer 8007 outside the third edge; the first overlap layer 8010, located on the first side 8002, contacting the first passivation layer 8008, the first overlap layer 8010 includes a first raised portion (unmarked) and a first extension portion (unmarked), the first raised portion protrudes relative to the first extension portion, the first raised portion is located inside the resonant region 8100, and overlaps with the first electrode layer 8004 on the first edge side, the first raised portion and the first electrode layer 8004 are located on both sides of the first passivation layer 8008, the first extension portion is located outside the resonant region 8100, outside the first edge, and does not overlap with the first electrode layer 8004, the first extension portion and the piezoelectric layer 8001 include a first slot 8015;The second overlap layer 8011, located on the second side 8003, contacts the second passivation layer 8009. The second overlap layer 8011 includes a second raised portion (unmarked) and a second extended portion (unmarked). The second raised portion protrudes relative to the second extended portion. The second raised portion is located inside the resonant region 8100 and overlaps with the second electrode layer 8006 on the fourth edge side. The second raised portion and the second electrode layer 8006 are located on opposite sides of the second passivation layer 8009. The second extended portion is located outside the resonant region 8100, outside the fourth edge, and does not overlap with the second electrode layer 8006. A second slot 8016 is included between the second extended portion and the piezoelectric layer 8001.

[0166] In this embodiment, the material of the piezoelectric layer 8001 includes, but is not limited to, one of the following: aluminum nitride, aluminum nitride alloy, gallium nitride, zinc oxide, lithium tantalate, lithium niobate, lead zirconate titanate, lead magnesium niobate-lead titanate.

[0167] In this embodiment, the piezoelectric layer 8001 is a flat layer, and the piezoelectric layer 8001 includes multiple grains, including a first grain and a second grain, wherein the first grain and the second grain are any two grains among the multiple grains. Those skilled in the art will understand that the crystal orientation, crystal plane, etc., of grains can be represented based on a coordinate system.

[0168] In this embodiment, the first grain can be represented based on a first three-dimensional coordinate system, and the second grain can be represented based on a second three-dimensional coordinate system. The first three-dimensional coordinate system includes at least a first coordinate axis along a first direction and a third coordinate axis along a third direction, and the second three-dimensional coordinate system includes at least a second coordinate axis along a second direction and a fourth coordinate axis along a fourth direction. The first coordinate axis corresponds to the height of the first grain, and the second coordinate axis corresponds to the height of the second grain.

[0169] In this embodiment, the first direction and the second direction are the same or opposite. It should be noted that the first direction and the second direction being the same means that the angle between the vector along the first direction and the vector along the second direction ranges from 0 degrees to 5 degrees; the first direction and the second direction being opposite means that the angle between the vector along the first direction and the vector along the second direction ranges from 175 degrees to 180 degrees.

[0170] In another embodiment, the first solid coordinate system is an ac solid coordinate system, wherein the first coordinate axis is a first c-axis and the third coordinate axis is a first a-axis; the second solid coordinate system is an ac solid coordinate system, wherein the second coordinate axis is a second c-axis and the fourth coordinate axis is a second a-axis, wherein the first c-axis and the second c-axis point in the same or opposite directions.

[0171] In another embodiment, the first solid coordinate system further includes a fifth coordinate axis along a fifth direction, and the second solid coordinate system further includes a sixth coordinate axis along a sixth direction. In another embodiment, the first direction and the second direction are the same or opposite, and the third direction and the fourth direction are the same or opposite. It should be noted that the third direction and the fourth direction being the same means that the angle between the vector along the third direction and the vector along the fourth direction ranges from 0 degrees to 5 degrees; the third direction and the fourth direction being opposite means that the angle between the vector along the third direction and the vector along the fourth direction ranges from 175 degrees to 180 degrees.

[0172] In another embodiment, the first solid coordinate system is an xyz solid coordinate system, wherein the first coordinate axis is the first z-axis, the third coordinate axis is the first y-axis, and the fifth coordinate axis is the first x-axis; the second solid coordinate system is an xyz solid coordinate system, wherein the second coordinate axis is the second z-axis, the fourth coordinate axis is the second y-axis, and the sixth coordinate axis is the second x-axis. In another embodiment, the first z-axis and the second z-axis point in the same direction, and the first y-axis and the second y-axis point in the same direction. In another embodiment, the first z-axis and the second z-axis point in opposite directions, and the first y-axis and the second y-axis point in opposite directions. In another embodiment, the first z-axis and the second z-axis point in the same direction, and the first y-axis and the second y-axis point in opposite directions. In another embodiment, the first z-axis and the second z-axis point in opposite directions, and the first y-axis and the second y-axis point in the same direction.

[0173] In this embodiment, the piezoelectric layer 8001 includes multiple grains, and the rocking curve of the crystal formed by the multiple grains has a full width at half maximum (FWHM) of less than 2.5 degrees.

[0174] In this embodiment, the material of the first electrode layer 8004 includes, but is not limited to, at least one of the following: molybdenum, ruthenium, tungsten, platinum, iridium, aluminum, and beryllium. The material of the first electrode extension layer 8005 includes, but is not limited to, at least one of the following: molybdenum, ruthenium, tungsten, platinum, iridium, aluminum, beryllium, copper, and gold. In this embodiment, the material of the first electrode layer 8004 is the same as the material of the first electrode extension layer 8005.

[0175] In this embodiment, the material of the second electrode layer 8006 includes, but is not limited to, at least one of the following: molybdenum, ruthenium, tungsten, platinum, iridium, aluminum, and beryllium. The material of the second electrode extension layer 8007 includes, but is not limited to, at least one of the following: molybdenum, ruthenium, tungsten, platinum, iridium, aluminum, beryllium, copper, and gold. In this embodiment, the material of the second electrode layer 8006 is the same as the material of the second electrode extension layer 8007.

[0176] In another embodiment, the material of the electrode layer may be different from the material of the electrode extension layer.

[0177] In this embodiment, the material of the first passivation layer 8008 includes, but is not limited to, one of the following: silicon dioxide, silicon oxynitride, silicon oxycarbide, silicon nitride, titanium oxide, aluminum oxide, hafnium silicate, zirconium silicate, hafnium dioxide, and zirconium dioxide. In this embodiment, the material of the second passivation layer 8009 includes, but is not limited to, one of the following: silicon dioxide, silicon oxynitride, silicon oxycarbide, silicon nitride, titanium oxide, aluminum oxide, hafnium silicate, zirconium silicate, hafnium dioxide, and zirconium dioxide. In this embodiment, the material of the first passivation layer 8008 is the same as the material of the second passivation layer 8009. In another embodiment, the materials of the first passivation layer (e.g., the first passivation layer 8008) and the second passivation layer (e.g., the second passivation layer 8009) may be different.

[0178] In this embodiment, the material of the first edge layer 8010 includes, but is not limited to, at least one of the following: molybdenum, ruthenium, tungsten, platinum, iridium, aluminum, and beryllium. In this embodiment, the material of the first edge layer 8010 is the same as the material of the electrode 8004.

[0179] In this embodiment, the material of the second edge layer 8011 includes, but is not limited to, at least one of the following: molybdenum, ruthenium, tungsten, platinum, iridium, aluminum, and beryllium. In this embodiment, the material of the second edge layer 8011 is the same as the material of the electrode 8006.

[0180] In another embodiment, the material of the edge layer can be different from that of the electrode layer. For example, the material of the edge layer is tungsten or platinum, and the material of the electrode layer is molybdenum.

[0181] In another embodiment, the overlap layer includes a first overlap sub-layer and a second overlap sub-layer, the first overlap sub-layer contacting the passivation layer, the second overlap sub-layer contacting the first overlap layer, the second overlap sub-layer and the passivation layer being located on opposite sides of the first overlap layer, the material of the first overlap sub-layer being different from the material of the second overlap layer, for example, the material of the first overlap layer being molybdenum, and the material of the second overlap layer being platinum or tungsten.

[0182] In this embodiment, the bulk acoustic wave resonator 8000 further includes: a first passive structure 8012 located on the first side 8002, contacting the first edge of the first electrode layer 8004; the first passive structure 8012 includes a first edge layer 8010, a first dielectric portion (unmarked) overlapping the first edge layer 8010 on the first passivation layer 8008, and a first slot 8015; and a second passive structure 8013 located on the second side 8003, contacting the fourth edge of the second electrode layer 8006; the second passive structure 8013 includes a second edge layer 8011, a second dielectric portion (unmarked) overlapping the second edge layer 8011 on the second passivation layer 8009, and a second slot 8016. It should be noted that the dielectric portion can electrically isolate the electrode layer and the edge layer, preventing them from conducting, thus the edge layer is passive, and the combined structure of the dielectric portion and the edge layer is also passive.

[0183] In this embodiment, the first thickness of the first passive structure 8012 is less than the thickness of the first electrode layer 8004, the second thickness of the second passive structure 8013 is less than the thickness of the second electrode layer 8006, and the first thickness is equal to or approximately equal to the second thickness.

[0184] In this embodiment, the first width of the first raised portion matches the wavelength of the transverse acoustic wave dominant mode generated by the resonant region 8100 (e.g., the first width is an integer multiple of half the wavelength), and the second width of the second raised portion matches the wavelength of the transverse acoustic wave dominant mode generated by the resonant region 8100 (e.g., the second width is an integer multiple of half the wavelength). The first width is equal to or approximately equal to the second width. It should be noted that the first and second raised portions are used to match the acoustic impedance of the resonant region and the attenuation region, thereby allowing more acoustic waves generated by the resonant region to propagate into the attenuation region.

[0185] In this embodiment, the third thickness of the first extension is less than the thickness of the first electrode layer 8004, the fourth thickness of the second extension is less than the thickness of the second electrode layer 8006, and the third thickness is equal to or approximately equal to the fourth thickness.

[0186] In this embodiment, the overlapping area of ​​the first extension, the second electrode extension layer 8007, and the piezoelectric layer 8001 is the attenuation region 8200; the overlapping area of ​​the second extension, the first electrode extension layer 8005, and the piezoelectric layer 8001 is the attenuation region 8300; the first cutoff frequency of the attenuation region 8200 matches (for example, is equal to or less than) the cutoff frequency of the resonant region 8100, the second cutoff frequency of the attenuation region 8300 matches (for example, is equal to or less than) the cutoff frequency of the resonant region 8100, and the first cutoff frequency is equal to or approximately equal to the second cutoff frequency.

[0187] It should be noted that matching the cutoff frequency of the attenuation region with the cutoff frequency of the resonant region allows the sound wave entering the attenuation region to exhibit a decaying mode; that is, the wavenumber within the attenuation region contains only the imaginary part, resulting in exponential decay of the sound wave. Therefore, the passive structure can attenuate the laterally propagating sound wave generated in the resonant region, suppress parasitic edge modes, and improve Z-axis performance. p and the corresponding Q value. Furthermore, the passive structure has no electrical connection to the electrode layer, therefore the passive structure is related to Kt. 2 The impact is relatively small.

[0188] In this embodiment, the bulk acoustic resonator 8000 further includes: a cavity 8014, the first electrode layer 8004 located within the cavity 8014, one end of the first electrode extension layer 8005 located within the cavity 8014, and the first passive structure 8012 located within the cavity 8014. In another embodiment, the lower electrode layer (e.g., the first electrode layer 8004) may be located above the cavity, covering the cavity; the passive structure corresponding to the lower electrode is located outside the cavity.

[0189] Figure 18 This is a cross-sectional structural diagram of a bulk acoustic resonator 8000 according to an embodiment of the present invention.

[0190] like Figure 18As shown, the bulk acoustic wave resonator 8000 includes: a piezoelectric layer 8001, which includes a first side 8002 and a second side 8003; a first electrode layer 8004, located on the first side 8002 and in contact with the piezoelectric layer 8001, the first electrode layer 8004 further including a fifth edge and a sixth edge opposite to the fifth edge in the horizontal direction, the fifth edge being downsloping and the sixth edge being downsloping; and a second electrode layer 8006, located on the second side 8003 and in contact with the piezoelectric layer 8001, the second electrode layer 8006 further including a seventh edge and an eighth edge opposite to the seventh edge in the horizontal direction, the seventh edge being downsloping and the eighth edge being downsloping. The edge is sloping downwards; within the resonant region 8100, the fifth edge corresponds vertically to the seventh edge, and the sixth edge corresponds vertically to the eighth edge; the first passivation layer 8008 is located on the first side 8002, and the first passivation layer 8008 located inside the resonant region 8100 covers the first electrode layer 8004; the second passivation layer 8009 is located on the second side 8003, and the second passivation layer 8009 located inside the resonant region 8100 covers the second electrode layer 8006; the first overlap layer 8010 is located on the first side 8002, in contact with the first passivation layer 8008, and the first overlap layer 8010 includes the first raised portion (unmarked) and The first extension (not marked) has a raised portion that protrudes relative to it. The raised portion is located inside the resonant region 8100 and overlaps with the first electrode layer 8004 on the fifth and sixth edge sides. The raised portion and the first electrode layer 8004 are located on opposite sides of the first passivation layer 8008. The first extension is located outside the resonant region 8100 and also outside the fifth and sixth edges, without overlapping with the first electrode layer 8004. A first slot 8015 is included between the first extension and the piezoelectric layer 8001. The second overlap layer 8011 is located on the second side 8003 and contacts the second passivation layer. Layer 8009, the second overlap layer 8011 includes a second raised portion (unmarked) and a second extension portion (unmarked), the second raised portion protrudes relative to the second extension portion, the second raised portion is located inside the resonant region 8100, and also overlaps with the second electrode layer 8006 on the seventh edge side and the eighth edge side, the second raised portion and the second electrode layer 8006 are located on both sides of the second passivation layer 8009, the second extension portion is located outside the resonant region 8100, and also outside the seventh edge and the eighth edge, and does not overlap with the second electrode layer 8006, the second extension portion and the piezoelectric layer 8001 include a second slot 8016.

[0191] In this embodiment, the area where the first extension, the second extension, and the piezoelectric layer 8001 overlap is the attenuation region 8400; the third cutoff frequency of the attenuation region 8400 matches (for example, is equal to or less than) the cutoff frequency of the resonant region 8100.

[0192] In another embodiment, the bulk acoustic resonator includes: a piezoelectric layer comprising a first side and a second side perpendicular to the first side in a vertical direction; a first electrode layer located on the first side and in contact with the piezoelectric layer, the first electrode layer comprising a first edge and a second edge perpendicular to the first edge in a horizontal direction, the first edge being sloping downwards; a first electrode extension layer located on the first side, in contact with the piezoelectric layer and connected to the second edge; a second electrode layer located on the second side and in contact with the piezoelectric layer, the second electrode layer comprising a third edge and a fourth edge perpendicular to the third edge in a horizontal direction, the fourth edge being sloping downwards; a second electrode extension layer located on the second side, in contact with the piezoelectric layer and connected to the third edge; the overlapping region of the first electrode layer, the second electrode layer, and the piezoelectric layer is a resonant region, wherein the first edge corresponds to the third edge in a vertical direction, and the second edge corresponds to the fourth edge in a vertical direction; the first electrode extension layer and the second electrode extension layer are located outside the resonant region and have no overlapping portion; a first overlap layer located on the first side and in contact with the piezoelectric layer. The piezoelectric layer comprises a first edge layer including a first raised portion and a first extended portion. The first raised portion protrudes relative to the first extended portion and is located inside the resonant region, overlapping with the first electrode layer on the first edge side. A first dielectric portion (e.g., vacuum, air, helium) is included between the first raised portion and the first electrode layer. The first extended portion is located outside the resonant region and outside the first edge, without overlapping with the first electrode layer, and contacts the piezoelectric layer. A second edge layer is located on the second side and contacts the piezoelectric layer. The second edge layer includes a second raised portion and a second extended portion. The second raised portion protrudes relative to the second extended portion and is located inside the resonant region, overlapping with the second electrode layer on the fourth edge side. A second dielectric portion (e.g., vacuum, air, helium) is included between the second raised portion and the second electrode layer. The second extended portion is located outside the resonant region and outside the fourth edge, without overlapping with the second electrode layer, and contacts the piezoelectric layer.

[0193] In another embodiment described above, the bulk acoustic resonator further includes: a first passive structure located on the first side and in contact with the piezoelectric layer, the first passive structure including a first edge layer and a first dielectric portion; and a second passive structure located on the second side and in contact with the piezoelectric layer, the second passive structure including a second edge layer and a second dielectric portion. It should be noted that the dielectric portion can electrically isolate the electrode layer and the edge layer, preventing them from conducting, thereby making the edge layer passive.

[0194] In another embodiment described above, the region where the first extension, the second electrode extension layer, and the piezoelectric layer overlap is a first attenuation region; the region where the second extension, the first electrode extension layer, and the piezoelectric layer overlap is a second attenuation region; the first cutoff frequency of the first attenuation region matches (for example, is equal to or less than) the cutoff frequency of the resonant region, the second cutoff frequency of the second attenuation region matches (for example, is equal to or less than) the cutoff frequency of the resonant region, and the first cutoff frequency is equal to or approximately equal to the second cutoff frequency.

[0195] It should be noted that matching the cutoff frequency of the attenuation region with the cutoff frequency of the resonant region allows the sound wave entering the attenuation region to exhibit a decaying mode; that is, the wavenumber within the attenuation region contains only the imaginary part, resulting in exponential decay of the sound wave. Therefore, the passive structure can attenuate the laterally propagating sound wave generated in the resonant region, suppress parasitic edge modes, and improve Z-axis performance. p and the corresponding Q value. Furthermore, the passive structure has no electrical connection to the electrode layer, therefore the passive structure is related to Kt. 2 The impact is relatively small.

[0196] Figure 19 This is a structural schematic diagram of a wireless communication device 900. (See diagram below.) Figure 19As shown, the wireless communication device 900 includes: a radio frequency (RF) front-end device 910, a baseband processing device 930, and an antenna 950. A first end of the RF front-end device 910 is connected to the baseband processing device 930, and a second end of the RF front-end device 910 is connected to the antenna 950. The RF front-end device 910 includes: a first filter device 911, a second filter device 913, a multiplexing device 915, a power amplifier device 917, and a low-noise amplifier device 919. The first filter device 911 is connected to the power amplifier device 917; the second filter device 913 is electrically connected to the low-noise amplifier device 919; and the multiplexing device 915 includes at least one transmit filter device (not shown) and at least one receive filter device (not shown). The first filter device 911 includes at least one bulk acoustic wave resonator provided in one of the above embodiments, and the second filter device 913 includes at least one bulk acoustic wave resonator provided in one of the above embodiments. The at least one transmitting filter device includes at least one bulk acoustic resonator provided in one of the above embodiments, or the at least one receiving filter device includes at least one bulk acoustic resonator provided in one of the above embodiments.

[0197] Figure 20 A specific embodiment of the method for forming the bulk acoustic resonator of the present invention is shown, but the present invention may also be implemented in other ways different from those described herein, and therefore the present invention is not limited to the specific embodiments disclosed below.

[0198] Figure 20 This is a schematic flowchart of a method for forming a bulk acoustic resonator device according to an embodiment of the present invention.

[0199] This invention also provides a method 1000 for forming a bulk acoustic resonator, comprising:

[0200] S1001, a piezoelectric layer is formed, the piezoelectric layer including a first side and a second side opposite to the first side in a vertical direction; a first electrode layer is formed on the first side and in contact with the piezoelectric layer; a second electrode layer is formed on the second side and in contact with the piezoelectric layer; the region where the first electrode layer, the second electrode layer and the piezoelectric layer overlap is a resonant region;

[0201] S1003, a first passive structure is formed, located on the first side, and has a first overlapping portion with at least one edge of the first electrode layer. The first passive structure includes: a first raised portion, a first extended portion, and a first dielectric portion. The first raised portion protrudes relative to the first extended portion. The first raised portion is located inside the resonant region and has the first overlapping portion with at least one edge of the first electrode layer. The first raised portion is used to match the acoustic impedance of the resonant region and at least one attenuation region outside the resonant region, allowing more sound waves generated within the resonant region to enter the at least one attenuation region. The first dielectric portion is located between the first raised portion and the first electrode layer, used to electrically isolate the first electrode layer from the first passive structure. The first extended portion is located outside the resonant region and within the at least one attenuation region, used to attenuate sound waves entering the at least one attenuation region.

[0202] S1005, a second passive structure is formed, located on the second side, having a second overlap with at least one edge of the second electrode layer. The second passive structure includes: a second raised portion, a second extended portion, and a second dielectric portion. The second raised portion protrudes relative to the second extended portion. The second raised portion is located inside the resonant region and has a second overlap with at least one edge of the second electrode layer. The second raised portion is used to match the acoustic impedance of the resonant region and the at least one attenuation region, allowing more sound waves generated in the resonant region to enter the at least one attenuation region. The second dielectric portion is located between the second raised portion and the second electrode layer, used to electrically isolate the second electrode layer from the second passive structure. The second extended portion is located outside the resonant region and inside the at least one attenuation region, used to attenuate sound waves entering the at least one attenuation region.

[0203] In some embodiments, the first passive structure and the second passive structure surround the resonant region.

[0204] In some embodiments, the thickness of the first passive structure is equal to or less than the thickness of the first electrode layer, and the thickness of the second passive structure is equal to or less than the thickness of the second electrode layer.

[0205] In some embodiments, forming the first electrode layer includes forming at least one downsloping edge corresponding to the first passive structure, and forming the second electrode layer includes forming at least one downsloping edge corresponding to the second passive structure.

[0206] In some embodiments, forming the first passive structure includes: forming a first passivation layer located on the first side and covering the first electrode layer; forming a first overlap layer in contact with the first passivation layer, wherein the first overlap layer and at least one edge of the first electrode layer have the first overlapping portion; wherein the first passivation layer includes the first dielectric portion; wherein the first overlap layer includes the first raised portion and the first extension portion.

[0207] In some embodiments, forming the second passive structure includes: forming a second passivation layer located on the second side and covering the second electrode layer; forming a second overlap layer in contact with the second passivation layer, wherein the second overlap layer and at least one edge of the second electrode layer have a second overlapping portion; wherein the second passivation layer includes a second dielectric portion; wherein the second overlap layer includes a second raised portion and a second extension portion.

[0208] In some embodiments, the thickness of the first extension is less than the thickness of the first electrode layer, and the thickness of the second extension is less than the thickness of the second electrode layer.

[0209] In some embodiments, the at least one attenuation region includes a first attenuation region, the first cutoff frequency of the first attenuation region being equal to or less than the cutoff frequency of the resonant region, and the first attenuation region corresponding to the overlapping region of the first extension, the piezoelectric layer, and the second extension.

[0210] In some embodiments, the method of forming the bulk acoustic resonator further includes: forming a first electrode extension layer located on the first side and connected to the first electrode layer; and forming a second electrode extension layer located on the second side and connected to the second electrode layer.

[0211] In some embodiments, the at least one attenuation region includes a second attenuation region, the second cutoff frequency of the second attenuation region being equal to or less than the cutoff frequency of the resonant region, and the second attenuation region corresponding to the overlapping region of the second electrode extension layer, the piezoelectric layer and the first extension.

[0212] In some embodiments, the at least one attenuation region includes a third attenuation region, the third cutoff frequency of the third attenuation region being equal to or less than the cutoff frequency of the resonant region, and the third attenuation region corresponding to the overlapping region of the second extension, the piezoelectric layer and the first electrode extension layer.

[0213] In some embodiments, the width of the first raised portion is an integer multiple of half the wavelength of the sound wave generated in the resonant region, and the width of the second raised portion is an integer multiple of half the wavelength of the sound wave generated in the resonant region.

[0214] In some embodiments, forming the first overlap layer includes forming a first overlap sublayer and a second overlap layer, wherein the second overlap sublayer and the piezoelectric layer are located on opposite sides of the first overlap layer, and the material of the first overlap sublayer is different from the material of the second overlap layer.

[0215] In some embodiments, forming the second overlap layer includes forming a third overlap sub-layer and a fourth overlap sub-layer, wherein the fourth overlap sub-layer and the piezoelectric layer are located on opposite sides of the third overlap layer, and the material of the third overlap layer is different from the material of the fourth overlap layer.

[0216] In some embodiments, the method of forming the bulk acoustic resonator further includes: forming a first sacrificial layer located between the first extension and the piezoelectric layer; and forming a second sacrificial layer located between the second extension and the piezoelectric layer.

[0217] In some embodiments, the method for forming the bulk acoustic resonator further includes: removing the first sacrificial layer to form a first slot located between the first extension and the piezoelectric layer; and removing the second sacrificial layer to form a second slot located between the second extension and the piezoelectric layer.

[0218] In some embodiments, the first dielectric portion is further located between the piezoelectric layer and the first extension portion, and the second dielectric portion is further located between the piezoelectric layer and the second extension portion.

[0219] In some embodiments, the method further includes: forming a third dielectric portion located on the second side and in contact with the second electrode layer; and forming a surrounding groove located within the third dielectric portion, inside the resonant region, inside the second raised portion, and adjacent to the second raised portion.

[0220] In some embodiments, the shape of the circumferential groove includes: a circle, an ellipse, or a polygon.

[0221] In some embodiments, the method further includes: forming a third dielectric portion located on the first side and in contact with the first electrode layer; and forming a surrounding groove located within the third dielectric portion, inside the resonant region, inside the first raised portion, and adjacent to the first raised portion.

[0222] In some embodiments, the shape of the circumferential groove includes: a circle, an ellipse, or a polygon.

[0223] It should be noted that the raised portion of the passive structure is located inside the resonant region and overlaps with the electrode layer. This allows it to match the acoustic impedance of the resonant region and the attenuation region outside the resonant region, thereby allowing more sound waves generated in the resonant region to propagate into the attenuation region. Furthermore, the cutoff frequency of the attenuation region matches (e.g., is equal to or less than) the cutoff frequency of the resonant region, which can attenuate the sound waves entering the attenuation region, suppress parasitic edge modes, and improve Z-axis impedance. p and the corresponding Q value. The cutoff frequency is the frequency corresponding to 0 wavenumber on the dispersion curve. Furthermore, the passive structure is not electrically connected to the electrode layer; therefore, the passive structure has no effect on Kt. 2 The impact is relatively small.

[0224] Figures 21 to 24 A specific embodiment of the method for forming the bulk acoustic resonator of the present invention is shown, but the present invention may also be implemented in other ways different from those described herein, and therefore the present invention is not limited to the specific embodiments disclosed below.

[0225] Figures 21 to 24 This is a cross-sectional structural schematic diagram of a method for forming a bulk acoustic resonant device 1100 according to an embodiment of the present invention.

[0226] like Figure 21 As shown, the method for forming the bulk acoustic resonator 1100 includes: forming a piezoelectric layer 1101, the piezoelectric layer 1101 including a first side 1102 and a second side 1103 opposite to the first side 1102 in the vertical direction; forming a first electrode layer 1104 located on the first side 1102 and in contact with the piezoelectric layer 1101, the first electrode layer 1104 including a first edge and a second edge opposite to the first edge in the horizontal direction; forming a first electrode extension layer 1105 located on the first side 1102 and in contact with the piezoelectric layer 1101, the first electrode extension layer 1105 being connected to the second edge.

[0227] In this embodiment, the method for forming the bulk acoustic resonator 1100 further includes providing a first substrate (not shown) before forming the piezoelectric layer 1101. In this embodiment, the piezoelectric layer 1101 is formed on one side of the first substrate, and the first substrate is located on the second side 1103.

[0228] In this embodiment, forming the first electrode layer 1104 includes: forming a first downward sloped edge located at the first edge.

[0229] like Figure 22As shown, the method for forming the bulk acoustic resonator 1100 further includes: forming a first passivation layer 1106 located on the first side 1102, the first passivation layer 1106 covering the first electrode layer 1104, the first passivation layer 1106 also covering the piezoelectric layer 1101 on the outer side of the first edge, and the first passivation layer 1106 also covering the first electrode extension layer 1105 on the outer side of the second edge; forming a first overlap layer 1107 located on the first side 1102 and in contact with the first passivation layer 1106, the first overlap layer 1107 including... The first raised portion (unmarked) and the first extended portion (unmarked) are located on the inner side of the first edge and overlap with the first electrode layer 1104 on the first edge side. The first raised portion and the first electrode layer 1104 are located on both sides of the first passivation layer 1106. The first extended portion is located on the outer side of the first edge and does not overlap with the first electrode layer 1104. The first extended portion and the piezoelectric layer 1101 are located on both sides of the first passivation layer 1106 in the vertical direction.

[0230] In this embodiment, the method of forming the bulk acoustic resonator 1100 further includes: forming a sacrificial layer 1108 located on the first side 1102, covering the first electrode layer 1104, one end of the first electrode extension layer 1105 connected to the second edge, and the first overlap layer 1107, wherein the first passivation layer 1106 is included between the sacrificial layer 1108 and the first electrode layer 1104 and the first electrode extension layer 1105.

[0231] In this embodiment, the method for forming the bulk acoustic resonator 1100 further includes: forming a first connecting layer (not shown) located on the first side 1102, covering the sacrificial layer 1108 and the first passivation layer 1106.

[0232] In another embodiment, the method of forming a bulk acoustic resonator further includes: forming a sacrificial layer having an overlap with a first electrode layer, wherein a first passivation layer is included between the sacrificial layer and the first electrode layer, a first overlap layer corresponding to the first electrode layer is located on a first side in the horizontal direction of the sacrificial layer, and a first electrode extension layer is located on a second side in the horizontal direction of the sacrificial layer; and forming a connecting layer covering the sacrificial layer and the first passivation layer.

[0233] In this embodiment, the method for forming the bulk acoustic resonator 1100 further includes: providing a second substrate (not shown); forming a second connecting layer (not shown) located on one side of the second substrate and covering the second substrate; bonding the first connecting layer and the second connecting layer to form an intermediate layer (not shown), wherein the second substrate and the intermediate layer are located on the first side 1102; and removing the first substrate. In this embodiment, bonding the first connecting layer and the second connecting layer includes: bonding the first connecting layer and the second connecting layer or adhering the first connecting layer and the second connecting layer.

[0234] like Figure 23 As shown, the method for forming the bulk acoustic resonator 1100 further includes: forming a second electrode layer 1109 located on the second side 1103 and in contact with the piezoelectric layer 1101, wherein the second electrode layer 1109 includes a third edge and a fourth edge opposite to the third edge in the horizontal direction; forming a second electrode extension layer 1110 located on the second side 1103 and in contact with the piezoelectric layer 1101, wherein the second electrode extension layer 1110 is connected to the third edge of the second electrode layer 1109, wherein the third edge corresponds to the first edge in the vertical direction and the fourth edge corresponds to the second edge in the vertical direction.

[0235] In this embodiment, forming the second electrode layer 1109 includes forming a second downward sloped edge located at the fourth edge.

[0236] like Figure 24 As shown, the method for forming the bulk acoustic resonator 1100 further includes: forming a second passivation layer 1111 located on the second side 1103, the second passivation layer 1111 covering the second electrode layer 1109, the second passivation layer 1111 also covering the piezoelectric layer 1101 on the outer side of the fourth edge, and the second passivation layer 1111 also covering the second electrode extension layer 1110 on the outer side of the third edge; forming a second overlap layer 1112 located on the second side 1103, contacting the second passivation layer 1111, the second overlap layer 1112 including... The second raised portion (unmarked) and the second extended portion (unmarked) are located on the inner side of the fourth edge and overlap with the second electrode layer 1109 on the fourth edge side. The second raised portion and the second electrode layer 1109 are located on both sides of the second passivation layer 1111. The second extended portion is located on the outer side of the fourth edge and does not overlap with the second electrode layer 1109. The second extended portion and the piezoelectric layer 1101 are located on both sides of the second passivation layer 1111 in the vertical direction.

[0237] In this embodiment, the method for forming the bulk acoustic resonator 1100 further includes: removing the sacrificial layer 1108 to form a cavity 1113, wherein the first electrode layer 1104, one end of the first electrode extension layer 1105 connected to the second edge, and the first edge layer 1107 are located in the cavity 1113.

[0238] In this embodiment, a first passive structure 1114 is formed on the first overlap layer 1107 and the first passivation layer 1106, where the first dielectric portion (not labeled) overlaps with the first overlap layer 1107. This structure is located on the first side 1102 and contacts the first edge of the first electrode layer 1104 and the piezoelectric layer 1101 outside the first edge. A second passive structure 1115 is formed on the second overlap layer 1112 and the second passivation layer 1111, where the second dielectric portion (not labeled) overlaps with the second overlap layer 1112. This structure is located on the second side 1103 and contacts the fourth edge of the second electrode layer 1109 and the piezoelectric layer 1101 outside the fourth edge. It should be noted that the dielectric portion can electrically isolate the electrode layer and the overlap layer, preventing them from conducting. Therefore, the overlap layer is passive, and the combined structure of the dielectric portion and the overlap layer is also passive.

[0239] In this embodiment, the first thickness of the first passive structure 1114 is less than the thickness of the first electrode layer 1104, the second thickness of the second passive structure 1115 is less than the thickness of the second electrode layer 1109, and the first thickness is equal to or approximately equal to the second thickness.

[0240] In this embodiment, the overlapping region of the first electrode layer 1104, the second electrode layer 1109, and the piezoelectric layer 1101 is the resonant region 1120; the overlapping region of the first extension, the second electrode extension layer 1110, and the piezoelectric layer 1101 is the attenuation region 1130; the overlapping region of the second extension, the first electrode extension layer 1105, and the piezoelectric layer 1101 is the attenuation region 1140; the first cutoff frequency of the attenuation region 1130 matches (e.g., is equal to or less than) the cutoff frequency of the resonant region 1120; the second cutoff frequency of the attenuation region 1140 matches (e.g., is equal to or less than) the cutoff frequency of the resonant region 1120; and the first cutoff frequency is equal to or approximately equal to the second cutoff frequency.

[0241] In this embodiment, the first width of the first raised portion matches the wavelength of the dominant transverse acoustic mode generated by the resonant region, such as the Rayleigh Lamb S1 mode or the TE1 mode (e.g., the first width is an integer multiple of half the wavelength), and the second width of the second raised portion matches the wavelength of the dominant transverse acoustic mode generated by the resonant region (e.g., the second width is an integer multiple of half the wavelength). The first width is equal to or approximately equal to the second width. It should be noted that the first and second raised portions are used to match the acoustic impedance of the resonant region and the attenuation region, thereby allowing more acoustic waves generated by the resonant region to propagate into the attenuation region.

[0242] In this embodiment, the third thickness of the first extension is less than the thickness of the first electrode layer 1104, the fourth thickness of the second extension is less than the thickness of the second electrode layer 1109, and the third thickness is equal to or approximately equal to the fourth thickness.

[0243] It should be noted that matching the cutoff frequency of the attenuation region with the cutoff frequency of the resonant region allows the sound wave entering the attenuation region to exhibit an attenuated mode. That is, the wavenumber in the attenuation region only contains the imaginary part, and the sound wave decays exponentially. This attenuates the transversely propagating sound wave generated in the resonant region, suppresses parasitic edge modes, and improves Z-axis performance. p and the corresponding Q value. Furthermore, the passive structure has no electrical connection to the electrode layer, therefore the passive structure is related to Kt. 2 The impact is relatively small.

[0244] In another embodiment, forming an overlap layer includes: forming a first overlap sub-layer that contacts a passivation layer; forming a second overlap sub-layer that contacts the first overlap layer, wherein the passivation layer and the second overlap sub-layer are located on opposite sides of the first overlap layer, wherein the material of the first overlap sub-layer is different from the material of the second overlap layer, for example, the material of the first overlap layer is molybdenum, and the material of the second overlap layer is platinum or tungsten.

[0245] Figure 25 A specific embodiment of the method for forming the bulk acoustic resonator of the present invention is shown, but the present invention may also be implemented in other ways different from those described herein, and therefore the present invention is not limited to the specific embodiments disclosed below.

[0246] This embodiment further describes the bulk acoustic wave resonator 1100 based on the method for forming the bulk acoustic wave resonator 1100 described in the above embodiments. The difference between this embodiment and the above embodiments is that the bulk acoustic wave resonator 1100 also includes a third dielectric portion and a surrounding groove. A detailed description will follow with reference to the accompanying drawings.

[0247] like Figure 25 As shown, it should be noted that Figure 25Is Figure 24 Continuing from the above, the method of forming the bulk acoustic resonator 1100 further includes: forming a third dielectric portion (not shown) located on the second side 1103 and in contact with the second electrode layer 1109; and a surrounding groove 1116 located within the third dielectric portion, inside the resonant region 1120, inside the second raised portion, and adjacent to the second raised portion.

[0248] In this embodiment, the circumferential groove 1116 is polygonal. In other embodiments, the circumferential groove may also be circular or elliptical.

[0249] It should be noted that the second passivation layer 1111 includes the third dielectric portion and the second dielectric portion.

[0250] In this embodiment, by adding the surrounding groove 1116 inside the resonant region 1120, a first region I formed by the surrounding groove 1116 and a second region II formed by the first raised portion and the second raised portion are created. By setting the cutoff frequency of the first region I to be greater than the cutoff frequency of the middle portion (unmarked) of the resonant region 1120 inside the surrounding groove 1116, and setting the cutoff frequency of the second region II to be less than the cutoff frequency of the middle portion, a piston mode is formed. See [link to documentation]. Figure 25 The diagram shows the sound velocity distribution under piston mode. The sound velocity is proportional to the cutoff frequency. Exciting the piston mode can suppress higher-order parasitic modes of transverse sound waves, such as... Figure 32 As shown, reducing the series resonant frequency (f s (near and less than f) s Partial noise.

[0251] Figure 26 and Figure 27 A specific embodiment of the method for forming the bulk acoustic resonator of the present invention is shown, but the present invention may also be implemented in other ways different from those described herein, and therefore the present invention is not limited to the specific embodiments disclosed below.

[0252] This embodiment further describes the bulk acoustic wave resonator 1100 based on the method for forming the bulk acoustic wave resonator 1100 described in the above embodiments. The difference between this embodiment and the above embodiments is that the bulk acoustic wave resonator 1100 also includes a third dielectric portion and a surrounding groove. A detailed description will follow with reference to the accompanying drawings.

[0253] like Figure 26 As shown, it should be noted that Figure 26 Is Figure 22Continuing from the above, the method of forming the bulk acoustic resonator 1100 further includes: forming a third dielectric portion (not shown) located on the first side 1102 and in contact with the first electrode layer 1104; and a surrounding groove 1116 located within the third dielectric portion, inside the resonant region 1120, inside the first raised portion, and adjacent to the first raised portion.

[0254] In this embodiment, the circumferential groove 1116 is polygonal. In other embodiments, the circumferential groove may also be circular or elliptical.

[0255] It should be noted that the first passivation layer 1106 includes the third dielectric portion and the first dielectric portion.

[0256] It should be noted that after the formation of the circumferential groove, subsequent processes are the same as... Figure 23 and Figure 24 And the corresponding description is consistent, until the bulk acoustic resonator 1100 is formed (e.g. Figure 27 (As shown).

[0257] In this embodiment, by adding the surrounding groove 1116 inside the resonant region 1120, a first region I formed by the surrounding groove 1116 and a second region II formed by the first raised portion and the second raised portion are created. By setting the cutoff frequency of the first region I to be greater than the cutoff frequency of the middle portion (unmarked) of the resonant region 1120 inside the surrounding groove 1116, and setting the cutoff frequency of the second region II to be less than the cutoff frequency of the middle portion, a piston mode is formed. See [link to documentation]. Figure 11 The diagram shows the sound velocity distribution under piston mode. The sound velocity is proportional to the cutoff frequency. Exciting the piston mode can suppress higher-order parasitic modes of transverse sound waves, such as... Figure 32 As shown, reducing the series resonant frequency (f s (near and less than f) s Partial noise.

[0258] Figures 28 to 31 A specific embodiment of the method for forming the bulk acoustic resonator of the present invention is shown, but the present invention may also be implemented in other ways different from those described herein, and therefore the present invention is not limited to the specific embodiments disclosed below.

[0259] Figures 28 to 31 This is a cross-sectional structural schematic diagram of a method for forming a bulk acoustic resonator 1200 according to an embodiment of the present invention.

[0260] like Figure 28As shown, the method for forming the bulk acoustic resonator 1200 includes: forming a piezoelectric layer 1201, the piezoelectric layer 1201 including a first side 1202 and a second side 1203 opposite to the first side 1202 in a vertical direction; forming a first electrode layer 1204 located on the first side 1202 and in contact with the piezoelectric layer 1201, the first electrode layer 1204 including a first edge and a second edge opposite to the first edge in a horizontal direction; forming a first electrode extension layer 1205 located on the first side 1202 and in contact with the piezoelectric layer 1201, the first electrode extension layer 1205 being connected to the second edge.

[0261] In this embodiment, the method for forming the bulk acoustic resonator 1200 further includes providing a first substrate (not shown) before forming the piezoelectric layer 1201. In this embodiment, the piezoelectric layer 1201 is formed on one side of the first substrate, and the first substrate is located on the second side 1203.

[0262] In this embodiment, forming the first electrode layer 1204 includes: forming a first downward sloped edge located at the first edge.

[0263] like Figure 29 As shown, the method for forming the bulk acoustic resonator 1200 further includes: forming a first passivation layer 1206 located on the first side 1202, the first passivation layer 1206 covering the first electrode layer 1204 and also covering the first electrode extension layer 1205 outside the second edge; forming a first sacrificial layer 1207 located on the first side 1202, outside the first edge, and contacting the piezoelectric layer 1201 and the first passivation layer 1206; and forming a first overlap layer 1208 located on the first side 1202, and contacting the first passivation layer 1206 and the first sacrificial layer 1207. The first edge layer 1208 includes a first raised portion (unmarked) and a first extension portion (unmarked). The first raised portion protrudes relative to the first extension portion. The first raised portion is located inside the first edge and overlaps with the first electrode layer 1204 on the first edge side. The first raised portion and the first electrode layer 1204 are located on both sides of the first passivation layer 1206. The first extension portion is located outside the first edge and does not overlap with the first electrode layer 1204. The first extension portion and the piezoelectric layer 1201 are located on both sides of the first sacrificial layer 1207 in the vertical direction.

[0264] In this embodiment, the method of forming the bulk acoustic resonator 1200 further includes: forming a second sacrificial layer 1209 located on the first side 1202, covering the first electrode layer 1204, one end of the first electrode extension layer 1205 connected to the second edge, the first overlap layer 1208, and the first sacrificial layer 1207, wherein the second sacrificial layer 1209 and the first electrode layer 1204 and the first electrode extension layer 1205 include the first passivation layer 1206.

[0265] In this embodiment, the method for forming the bulk acoustic resonator 1200 further includes: forming a first connecting layer (not shown) located on the first side 1202, covering the second sacrificial layer 1209 and the piezoelectric layer 1201.

[0266] In this embodiment, the method for forming the bulk acoustic resonator 1200 further includes: providing a second substrate (not shown); forming a second connecting layer (not shown) located on one side of the second substrate and covering the second substrate; bonding the first connecting layer and the second connecting layer to form an intermediate layer (not shown), wherein the second substrate and the intermediate layer are located on the first side 1202; and removing the first substrate. In this embodiment, bonding the first connecting layer and the second connecting layer includes: bonding the first connecting layer and the second connecting layer or adhering the first connecting layer and the second connecting layer.

[0267] like Figure 30 As shown, the method for forming the bulk acoustic resonator 1200 further includes: forming a second electrode layer 1210 located on the second side 1203 and in contact with the piezoelectric layer 1201, wherein the second electrode layer 1210 includes a third edge and a fourth edge opposite to the third edge in the horizontal direction; forming a second electrode extension layer 1211 located on the second side 1203 and in contact with the piezoelectric layer 1201, wherein the second electrode extension layer 1211 is connected to the third edge of the second electrode layer 1210, wherein the third edge corresponds to the first edge in the vertical direction and the fourth edge corresponds to the second edge in the vertical direction.

[0268] In this embodiment, forming the second electrode layer 1210 includes forming a second downward sloped edge located at the fourth edge.

[0269] like Figure 31As shown, the method for forming the bulk acoustic resonator 1200 further includes: forming a second passivation layer 1212 located on the second side 1203, the second passivation layer 1212 covering the second electrode layer 1210 and also covering the second electrode extension layer 1211 outside the third edge; forming a slot sacrificial layer (not shown, for example, the first sacrificial layer 1207) located on the second side 1203, outside the fourth edge, contacting the piezoelectric layer 1201 and the second passivation layer 1212; and forming a second overlap layer 1213 located on the second side 1203, contacting the second passivation layer 1212. The second overlap layer 1213 includes a second raised portion (unmarked) and a second extension portion (unmarked). The second raised portion protrudes relative to the second extension portion. The second raised portion is located inside the fourth edge and overlaps with the second electrode layer 1210 on the fourth edge side. The second raised portion and the second electrode layer 1210 are located on both sides of the second passivation layer 1212. The second extension portion is located outside the fourth edge and does not overlap with the second electrode layer 1210. The second extension portion and the piezoelectric layer 1201 are located on both sides of the sacrificial layer in the vertical direction of the sacrificial layer.

[0270] In this embodiment, the method for forming the bulk acoustic resonator 1200 further includes: removing the second sacrificial layer 1209 to form a cavity 1214, wherein the first electrode layer 1204, one end of the first electrode extension layer 1205 connected to the second edge, and the first edge layer 1208 are located in the cavity 1214.

[0271] In this embodiment, the method for forming the bulk acoustic resonator 1200 further includes: removing the first sacrificial layer 1207 and the empty slot sacrificial layer to form the first empty slot 1215 and the second empty slot 1216 respectively.

[0272] In this embodiment, the first overlap layer 1208, the first dielectric portion (unmarked) overlapping the first passivation layer 1206, and the first slot 1215 form a first passive structure 1217, located on the first side 1202, contacting the first edge of the first electrode layer 1204; the second overlap layer 1213, the second dielectric portion (unmarked) overlapping the second passivation layer 1212, and the second slot 1216 form a second passive structure 1218, located on the second side 1203, contacting the fourth edge of the second electrode layer 1210. It should be noted that the dielectric portion can electrically isolate the electrode layer and the overlap layer, preventing them from conducting, thus making the overlap layer passive, and the combined structure of the dielectric portion and the overlap layer is also passive.

[0273] In this embodiment, the first thickness of the first passive structure 1217 is less than the thickness of the first electrode layer 1204, the second thickness of the second passive structure 1218 is less than the thickness of the second electrode layer 1210, and the first thickness is equal to or approximately equal to the second thickness.

[0274] In this embodiment, the overlapping region of the first electrode layer 1204, the second electrode layer 1210, and the piezoelectric layer 1201 is the resonant region 1220; the overlapping region of the first extension, the second electrode extension layer 1211, and the piezoelectric layer 1201 is the first attenuation region 1230; the overlapping region of the second extension, the first electrode extension layer 1205, and the piezoelectric layer 1201 is the second attenuation region 1240; the first cutoff frequency of the first attenuation region 1230 matches (e.g., is equal to or less than) the cutoff frequency of the resonant region 1220; the second cutoff frequency of the second attenuation region 1240 matches (e.g., is equal to or less than) the cutoff frequency of the resonant region 1220; and the first cutoff frequency is equal to or approximately equal to the second cutoff frequency.

[0275] In this embodiment, the first width of the first raised portion matches the wavelength of the transverse acoustic wave dominant mode generated by the resonant region 1220 (e.g., the first width is an integer multiple of half the wavelength), and the second width of the second raised portion matches the wavelength of the transverse acoustic wave dominant mode generated by the resonant region 1220 (e.g., the second width is an integer multiple of half the wavelength). The first width is equal to or approximately equal to the second width. It should be noted that the first and second raised portions are used to match the acoustic impedance of the resonant region and the attenuation region, thereby allowing more acoustic waves generated by the resonant region to propagate into the attenuation region.

[0276] In this embodiment, the third thickness of the first extension is less than the thickness of the first electrode layer 1204, the fourth thickness of the second extension is less than the thickness of the second electrode layer 1210, and the third thickness is equal to or approximately equal to the fourth thickness.

[0277] It should be noted that matching the cutoff frequency of the attenuation region with the cutoff frequency of the resonant region allows the sound wave entering the attenuation region to exhibit an attenuated mode. That is, the wavenumber in the attenuation region only contains the imaginary part, and the sound wave decays exponentially. This attenuates the transversely propagating sound wave generated in the resonant region, suppresses parasitic edge modes, and improves Z-axis performance. p and the corresponding Q value. Furthermore, the passive structure has no electrical connection to the electrode layer, therefore the passive structure is related to Kt. 2 The impact is relatively small.

[0278] In another embodiment, forming an overlap layer includes: forming a first overlap sub-layer that contacts a passivation layer; forming a second overlap sub-layer that contacts the first overlap layer, wherein the passivation layer and the second overlap sub-layer are located on opposite sides of the first overlap layer, wherein the material of the first overlap sub-layer is different from the material of the second overlap layer, for example, the material of the first overlap layer is molybdenum, and the material of the second overlap layer is platinum or tungsten.

[0279] In summary, the passive structure includes a raised portion located inside the resonant region, overlapping with the electrode layer. This allows for matching the acoustic impedance of the resonant region and the attenuation region, thereby enabling more sound waves generated in the resonant region to propagate into the attenuation region. Furthermore, the cutoff frequency of the attenuation region matches (e.g., is equal to or less than) the cutoff frequency of the resonant region, thus attenuating the sound waves entering the attenuation region, suppressing parasitic edge modes, and improving Z-axis impedance. p and the corresponding Q value. Furthermore, the passive structure is not electrically connected to the electrode layer, therefore the passive structure has no effect on Kt. 2 The impact is relatively small.

[0280] It should be understood that the examples and embodiments herein are merely exemplary, and those skilled in the art can make various modifications and corrections without departing from the spirit and scope of the invention as defined in this application and the appended claims.

Claims

1. A bulk acoustic resonant device, characterized in that, include: Cavity; A first electrode layer, at least one end of which is located above or inside the cavity; A piezoelectric layer, the piezoelectric layer including a first side and a second side opposite to the first side in a vertical direction, the cavity being located on the first side, the first electrode layer being located on the first side, and the first electrode layer contacting the piezoelectric layer; The second electrode layer is located on the second side and contacts the piezoelectric layer. The region where the first electrode layer, the second electrode layer, and the piezoelectric layer overlap is the resonant region. A first passive structure is located on the first side and has a first overlap with at least one edge of the first electrode layer; The first passive structure includes: a first raised portion located inside the resonant region, having a first overlapping portion with at least one edge of the first electrode layer, the first raised portion being used to match the acoustic impedance of the resonant region and at least one attenuation region outside the resonant region, allowing more sound waves generated in the resonant region to enter at least one attenuation region; a first dielectric portion located between the first raised portion and the first electrode layer, used to electrically isolate the first electrode layer from the first passive structure; and a first extension portion located outside the resonant region and within at least one attenuation region, used to attenuate sound waves entering at least one attenuation region, the first raised portion protruding relative to the first extension portion. The second passive structure is located on the second side and has a second overlap with at least one edge of the second electrode layer; The second passive structure includes: a second raised portion located inside the resonant region, having a second overlapping portion with at least one edge of the second electrode layer, the second raised portion being used to match the acoustic impedance of the resonant region and at least one attenuation region, allowing more sound waves generated in the resonant region to enter at least one attenuation region; a second dielectric portion located between the second raised portion and the second electrode layer, used to electrically isolate the second electrode layer and the second passive structure; and a second extension portion located outside the resonant region and within at least one attenuation region, used to attenuate sound waves entering at least one attenuation region, the second raised portion protruding relative to the second extension portion. A third dielectric portion and a surrounding groove located within the third dielectric portion, the surrounding groove being located inside the resonant region; wherein... The third dielectric portion is located on the second side and is in contact with the second electrode layer; the circumferential groove is located inside the second raised portion and is adjacent to the second raised portion. Alternatively, the third dielectric portion is located on the first side and is in contact with the first electrode layer; the circumferential groove is located inside the first raised portion and is adjacent to the first raised portion.

2. The bulk acoustic resonator as described in claim 1, characterized in that, The first passive structure and the second passive structure surround the resonant region.

3. The bulk acoustic resonator as described in claim 1, characterized in that, The thickness of the first passive structure is equal to or less than the thickness of the first electrode layer, and the thickness of the second passive structure is equal to or less than the thickness of the second electrode layer.

4. The bulk acoustic resonator as described in claim 1, characterized in that, At least one of the attenuation regions includes a first attenuation region, the first cutoff frequency of the first attenuation region being equal to or less than the cutoff frequency of the resonant region, and the first attenuation region corresponding to the overlapping area of ​​the first extension, the piezoelectric layer, and the second extension.

5. The bulk acoustic resonator as described in claim 1, characterized in that, Also includes: A first electrode extension layer is located on the first side and is connected to the first electrode layer; The second electrode extension layer is located on the second side and is connected to the second electrode layer.

6. The bulk acoustic resonator as described in claim 5, characterized in that, At least one of the attenuation regions includes a second attenuation region, the second cutoff frequency of the second attenuation region being equal to or less than the cutoff frequency of the resonant region, and the second attenuation region corresponding to the overlapping region of the second electrode extension layer, the piezoelectric layer, and the first extension.

7. The bulk acoustic resonator as described in claim 5, characterized in that, At least one of the attenuation regions includes a third attenuation region, the third cutoff frequency of which is equal to or less than the cutoff frequency of the resonant region, and the third attenuation region corresponds to the overlapping region of the second extension, the piezoelectric layer and the first electrode extension layer.

8. The bulk acoustic resonator as described in claim 1, characterized in that, At least one edge of the first electrode layer is sloping downwards, corresponding to the first passive structure, and at least one edge of the second electrode layer is sloping downwards, corresponding to the second passive structure.

9. The bulk acoustic resonator as described in claim 1, characterized in that, The width of the first raised portion is an integer multiple of half the wavelength of the sound wave generated in the resonant region, and the width of the second raised portion is an integer multiple of half the wavelength of the sound wave generated in the resonant region.

10. The bulk acoustic resonator as described in claim 1, characterized in that, The thickness of the first extension is less than the thickness of the first electrode layer, and the thickness of the second extension is less than the thickness of the second electrode layer.

11. The bulk acoustic resonator as described in claim 1, characterized in that, The first extension includes a first sub-part and a second sub-part, the second sub-part and the piezoelectric layer are located on opposite sides of the first sub-part, and the material of the first sub-part is different from that of the second sub-part.

12. The bulk acoustic resonator as described in claim 1, characterized in that, The second extension includes a third sub-part and a fourth sub-part, with the piezoelectric layer and the fourth sub-part located on opposite sides of the third sub-part, and the material of the third sub-part being different from that of the fourth sub-part.

13. The bulk acoustic resonator as described in claim 1, characterized in that, The first extension contacts the piezoelectric layer, and the second extension contacts the piezoelectric layer.

14. The bulk acoustic resonator as described in claim 1, characterized in that, The first dielectric portion is also located between the piezoelectric layer and the first extension portion, and the second dielectric portion is also located between the piezoelectric layer and the second extension portion.

15. The bulk acoustic resonator as described in claim 1, characterized in that, A first slot is included between the first extension and the piezoelectric layer, and a second slot is included between the piezoelectric layer and the second extension.

16. The bulk acoustic resonator as described in claim 1, characterized in that, The shape of the surrounding groove includes: circular, elliptical, or polygonal.

17. A filtering device, characterized in that, include: At least one bulk acoustic resonator as described in any one of claims 1 to 16.

18. A radio frequency front-end device, characterized in that, include: A power amplifier and at least one filter as described in claim 17; The power amplifier is connected to the filter.

19. A radio frequency front-end device, characterized in that, include: A low-noise amplifier and at least one filter as described in claim 17; The low-noise amplifier is connected to the filter.

20. A radio frequency front-end device, characterized in that, include: A multiplexing device, the multiplexing device comprising at least one filtering device as described in claim 17.

21. A method for forming a bulk acoustic resonator, characterized in that, include: A piezoelectric layer is formed, the piezoelectric layer including a first side and a second side opposite to the first side in a vertical direction; A first electrode layer is formed, located on the first side, and in contact with the piezoelectric layer; A second electrode layer is formed on the second side and contacts the piezoelectric layer. The region where the first electrode layer, the second electrode layer, and the piezoelectric layer overlap is the resonant region. A first passive structure is formed, located on the first side, and has a first overlap with at least one edge of the first electrode layer; The first passive structure includes: The system comprises a first raised portion, a first extended portion, and a first dielectric portion, wherein the first raised portion protrudes relative to the first extended portion; wherein the first raised portion is located inside the resonant region and has a first overlapping portion with at least one edge of the first electrode layer, and the first raised portion is used to match the acoustic impedance of the resonant region and at least one attenuation region outside the resonant region, so that more sound waves generated in the resonant region enter at least one attenuation region; the first dielectric portion is located between the first raised portion and the first electrode layer, and is used to electrically isolate the first electrode layer from the first passive structure; the first extended portion is located outside the resonant region and within at least one attenuation region, and is used to attenuate sound waves entering at least one attenuation region. A second passive structure is formed, located on the second side, and has a second overlap with at least one edge of the second electrode layer. The second passive structure includes: The system comprises a second raised portion, a second extended portion, and a second dielectric portion, wherein the second raised portion protrudes relative to the second extended portion; wherein the second raised portion is located inside the resonant region and has a second overlapping portion with at least one edge of the second electrode layer, and the second raised portion is used to match the acoustic impedance of the resonant region and at least one of the attenuation regions, so that more sound waves generated in the resonant region enter at least one of the attenuation regions; the second dielectric portion is located between the second raised portion and the second electrode layer, and is used to electrically isolate the second electrode layer from the second passive structure; the second extended portion is located outside the resonant region and within at least one of the attenuation regions, and is used to attenuate sound waves entering at least one of the attenuation regions; A third dielectric portion is formed; a surrounding groove is formed within the third dielectric portion, located inside the resonant region; wherein... The third dielectric portion is located on the second side and is in contact with the second electrode layer; the circumferential groove is located inside the second raised portion and is adjacent to the second raised portion. Alternatively, the third dielectric portion is located on the first side and is in contact with the first electrode layer; the circumferential groove is located inside the first raised portion and is adjacent to the first raised portion.

22. The method for forming a bulk acoustic resonator as described in claim 21, characterized in that, The first passive structure and the second passive structure surround the resonant region.

23. The method for forming a bulk acoustic resonator as described in claim 21, characterized in that, The thickness of the first passive structure is equal to or less than the thickness of the first electrode layer, and the thickness of the second passive structure is equal to or less than the thickness of the second electrode layer.

24. The method for forming a bulk acoustic resonator as described in claim 21, characterized in that, Forming the first electrode layer includes forming at least one downsloping edge corresponding to the first passive structure, and forming the second electrode layer includes forming at least one downsloping edge corresponding to the second passive structure.

25. The method for forming a bulk acoustic resonator as described in claim 21, characterized in that, Forming the first passive structure includes: forming a first passivation layer located on the first side and covering the first electrode layer; forming a first overlap layer in contact with the first passivation layer, wherein the first overlap layer and at least one edge of the first electrode layer have a first overlapping portion; wherein the first passivation layer includes the first dielectric portion; wherein the first overlap layer includes the first raised portion and the first extended portion.

26. The method for forming a bulk acoustic resonator as described in claim 21, characterized in that, Forming the second passive structure includes: forming a second passivation layer located on the second side and covering the second electrode layer; forming a second overlap layer in contact with the second passivation layer, wherein at least one edge of the second overlap layer and the second electrode layer has a second overlapping portion; wherein the second passivation layer includes a second dielectric portion; wherein the second overlap layer includes a second raised portion and a second extended portion.

27. The method for forming a bulk acoustic resonator as described in claim 21, characterized in that, The thickness of the first extension is less than the thickness of the first electrode layer, and the thickness of the second extension is less than the thickness of the second electrode layer.

28. The method for forming a bulk acoustic resonator as described in claim 21, characterized in that, At least one of the attenuation regions includes a first attenuation region, the first cutoff frequency of the first attenuation region being equal to or less than the cutoff frequency of the resonant region, and the first attenuation region corresponding to the overlapping area of ​​the first extension, the piezoelectric layer, and the second extension.

29. The method for forming a bulk acoustic resonator as described in claim 21, characterized in that, Also includes: A first electrode extension layer is formed, located on the first side, and connected to the first electrode layer; A second electrode extension layer is formed, located on the second side, and connected to the second electrode layer.

30. The method for forming a bulk acoustic resonator as described in claim 29, characterized in that, At least one of the attenuation regions includes a second attenuation region, the second cutoff frequency of the second attenuation region being equal to or less than the cutoff frequency of the resonant region, and the second attenuation region corresponding to the overlapping region of the second electrode extension layer, the piezoelectric layer, and the first extension.

31. The method for forming a bulk acoustic resonator as described in claim 29, characterized in that, At least one of the attenuation regions includes a third attenuation region, the third cutoff frequency of which is equal to or less than the cutoff frequency of the resonant region, and the third attenuation region corresponds to the overlapping region of the second extension, the piezoelectric layer and the first electrode extension layer.

32. The method for forming a bulk acoustic resonator as described in claim 21, characterized in that, The width of the first raised portion is an integer multiple of half the wavelength of the sound wave generated in the resonant region, and the width of the second raised portion is an integer multiple of half the wavelength of the sound wave generated in the resonant region.

33. The method for forming a bulk acoustic resonator as described in claim 25, characterized in that, Forming the first edge layer includes forming a first edge sub-layer and a second edge layer, wherein the second edge sub-layer and the piezoelectric layer are located on opposite sides of the first edge layer, and the materials of the first edge sub-layer and the second edge layer are different.

34. The method for forming a bulk acoustic resonator as described in claim 26, characterized in that, Forming the second edge layer includes forming a third edge sub-layer and a fourth edge sub-layer, wherein the fourth edge sub-layer and the piezoelectric layer are located on opposite sides of the third edge layer, and the material of the third edge layer is different from that of the fourth edge layer.

35. The method for forming a bulk acoustic resonator as described in claim 21, characterized in that, Also includes: A first sacrificial layer is formed between the first extension and the piezoelectric layer; A second sacrificial layer is formed between the second extension and the piezoelectric layer.

36. The method for forming a bulk acoustic resonator as described in claim 35, characterized in that, Also includes: Remove the first sacrificial layer to form a first vacancy, located between the first extension and the piezoelectric layer; The second sacrificial layer is removed to form a second void located between the second extension and the piezoelectric layer.

37. The method for forming a bulk acoustic resonator as described in claim 21, characterized in that, The first dielectric portion is also located between the piezoelectric layer and the first extension portion, and the second dielectric portion is also located between the piezoelectric layer and the second extension portion.

38. The method for forming a bulk acoustic resonator as described in claim 21, characterized in that, The shape of the surrounding groove includes: circular, elliptical, or polygonal.

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