Elastic wave resonator, elastic wave filter, wave divider, communication device

Abstract

In the same elastic wave resonator, the strength of the spurious is reduced while maintaining the uniformity of the resonance frequency. An elastic wave resonator (4) includes: a piezoelectric body (6); and, a plurality of electrode fingers (14, 22) arranged on the piezoelectric body in a propagation direction (TD) of an elastic wave. The area where the plurality of electrode fingers are located includes a first area (24A) and a second area (24B) when viewed from above. The plurality of electrode fingers include: a first electrode finger group (14A) located in the first area and a second electrode finger group (14B) located in the second area; the pitch (PA) of the first electrode finger group is different from the pitch (PB) of the second electrode finger group. The first area and the second area have frequency action characteristics that act in a direction in which the effect of the height of the resonance frequency or the anti-resonance frequency caused by the size relationship of the pitch of each electrode finger group is eliminated.

Description

Technical Field

[0001] This invention relates to elastic wave devices. Background Technology

[0002] Existing document 1 describes an elastic wave filter, which includes multiple interdigital transducers located on a piezoelectric substrate and having a specific resonant frequency.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: International Publication No. WO2005 / 050837 Summary of the Invention

[0006] The problem the invention aims to solve

[0007] In the conventional elastic wave filter described in Patent Document 1, there is a problem of stray oscillations occurring at frequencies different from the resonant frequency of the main resonance.

[0008] The means used to solve the problem

[0009] One embodiment of the elastic wave resonator disclosed herein includes: a piezoelectric body; and a plurality of electrode fingers located on the piezoelectric body and arranged in the direction of propagation of the elastic wave; the region where the plurality of electrode fingers are located includes a first region and a second region when viewed from above; the plurality of electrode fingers includes: a first electrode finger group located in the first region and a second electrode finger group located in the second region; the spacing of the first electrode finger group is different from the spacing of the second electrode finger group; the first region and the second region have frequency action characteristics that act in a direction that eliminates the effect of the magnitude relationship between the resonant frequency and the anti-resonant frequency caused by the magnitude relationship of the spacing of each electrode finger group.

[0010] Invention Effects

[0011] According to this disclosure, within the same elastic wave resonator, the intensity of stray waves is reduced while maintaining a uniform resonant frequency. Attached Figure Description

[0012] Figure 1 This is a schematic top view of an elastic wave resonator according to Embodiment 1 of this disclosure.

[0013] Figure 2 This is a schematic cross-sectional view of an elastic wave resonator according to Embodiment 1 of this disclosure.

[0014] Figure 3 This is a graph showing the relationship between the spacing and the duty cycle in the elastic wave resonator of Embodiment 1 of this disclosure, when the resonant frequency is constant.

[0015] Figure 4 This is a graph showing the characteristic of the elastic wave resonator of Embodiment 1 of this disclosure as a function of duty cycle.

[0016] Figure 5 This is a graph showing the relationship between the spacing and duty cycle and the frequency of the oscillating elastic wave in the elastic wave resonator of Embodiment 1 of this disclosure.

[0017] Figure 6 This is a schematic top view of the elastic wave resonator according to Embodiment 2 of this disclosure.

[0018] Figure 7 This is a schematic cross-sectional view of the elastic wave resonator according to Embodiment 2 of this disclosure.

[0019] Figure 8 This is a diagram illustrating the characteristics of the elastic wave resonator according to Embodiment 2 of this disclosure.

[0020] Figure 9 Other diagrams illustrating the characteristics of the elastic wave resonator according to Embodiment 2 of this disclosure.

[0021] Figure 10 This is a diagram showing the characteristics of the elastic wave resonator according to Embodiment 2 of this disclosure, when the maximum and minimum values ​​of the duty cycle are changed.

[0022] Figure 11 This is a graph showing the change in the duty cycle of the electrode fingers of the elastic wave resonator according to Embodiment 2 of this disclosure.

[0023] Figure 12 This is a schematic top view illustrating another example of an elastic wave resonator according to Embodiment 2 of this disclosure.

[0024] Figure 13 This is a diagram illustrating another example of the change in the duty cycle of the electrode fingers of the elastic wave resonator according to Embodiment 2 of this disclosure.

[0025] Figure 14 This is a bubble diagram illustrating an example of the intensity of the resonant wave generated in the elastic wave resonator according to Embodiment 2 of this disclosure.

[0026] Figure 15 This is another bubble diagram illustrating an example of the intensity of the resonant wave generated in the elastic wave resonator of Embodiment 2 of this disclosure.

[0027] Figure 16 This is another bubble diagram illustrating an example of the intensity of the resonant wave generated in the elastic wave resonator of Embodiment 2 of this disclosure.

[0028] Figure 17This is another bubble diagram illustrating an example of the intensity of the resonant wave generated in the elastic wave resonator of Embodiment 2 of this disclosure.

[0029] Figure 18 This is a diagram showing the characteristics of the elastic wave resonator according to Embodiment 2 and its variations, when the duty cycle of the electrode fingers is changed.

[0030] Figure 19 This is a schematic cross-sectional view of the elastic wave resonator according to Embodiment 3 of this disclosure.

[0031] Figure 20 This is a graph showing the relationship between the thickness of the electrode fingers and the resonant frequency of the elastic wave resonator according to Embodiment 3 of this disclosure.

[0032] Figure 21 This is a schematic cross-sectional view of the elastic wave resonator according to Embodiment 4 of this disclosure.

[0033] Figure 22 This is a graph showing the relationship between the thickness of the piezoelectric element and the resonant frequency of the elastic wave resonator according to Embodiment 4 of this disclosure.

[0034] Figure 23 This is a schematic cross-sectional view of the elastic wave resonator according to Embodiment 5 of this disclosure.

[0035] Figure 24 This is a graph showing the relationship between the thickness of the multilayer film and the resonant frequency of the elastic wave resonator according to Embodiment 5 of this disclosure.

[0036] Figure 25 This is a schematic cross-sectional view of the elastic wave resonator according to Embodiment Six of this disclosure.

[0037] Figure 26 This is a graph showing the relationship between the thickness of the protective layer and the resonant frequency of the elastic wave resonator according to Embodiment Six of this disclosure.

[0038] Figure 27 This is a schematic top view showing an enlarged view of the vicinity of the reflector of the elastic wave resonator of Embodiment Seven of this disclosure.

[0039] Figure 28 This is a schematic diagram illustrating the communication device of various embodiments of the present disclosure.

[0040] Figure 29 This is a circuit diagram illustrating the various embodiments of the demultiplexer disclosed herein. Detailed Implementation

[0041] [Implementation Method 1]

[0042] Embodiments of the present disclosure will now be described with reference to the accompanying drawings. Furthermore, the drawings used in the following description are schematic diagrams and do not strictly represent the dimensions of the components in the drawings to scale.

[0043] <Structure of a Resonator>

[0044] The elastic wave filter of this embodiment includes at least one elastic wave resonator. For example, the elastic wave filter is configured as a trapezoidal filter by connecting multiple elastic wave resonators in a trapezoidal shape. The elastic wave filter of this embodiment may also include multiple elastic wave resonators arranged in parallel in a direction orthogonal to the propagation direction of the elastic wave in each elastic wave resonator.

[0045] The following is for reference Figure 1 as well as Figure 2 The elastic wave resonator 4 of this embodiment will be described in more detail. Figure 1 This is a schematic top view of the elastic wave resonator 4 in this embodiment. Figure 2 This is a schematic cross-sectional view of the elastic wave resonator 4 in this embodiment, along... Figure 1 A cross-sectional view of the BB line. Furthermore, in this specification, the propagation direction TD of the elastic wave in the elastic wave resonator 4 is defined as including... Figure 1 In the top view of the elastic wave resonator 4, it is positioned vertically towards the plane of the paper, including... Figure 2 In the cross-sectional view of the elastic wave resonator 4, it is positioned in the left-right direction facing the plane of the paper. Furthermore, in this specification, including... Figure 2 In the cross-sectional view of the elastic wave resonator 4, only the components in the cross section are shown for the sake of simplicity, and the components inside the cross section are omitted.

[0046] like Figure 1 and Figure 2 As shown, the elastic wave resonator 4 of this embodiment includes at least: a piezoelectric element 6; and an IDT electrode 8 on the piezoelectric element 6. Furthermore, this specification includes... Figure 2 In the cross-sectional view of the elastic wave resonator 4, the IDT electrode 8 is shown positioned on the upper side facing the paper relative to the piezoelectric body 6.

[0047] The piezoelectric element 6 is made of a piezoelectric material, such as a single crystal of lithium tantalate (hereinafter also referred to as LT), lithium niobate, etc. In the elastic wave resonator 4, by applying a voltage to the conductive layer including the IDT electrode 8 described later, an elastic wave propagating in the propagation direction TD within the piezoelectric element 6 is excited. In this embodiment, as... Figure 2 As shown, the piezoelectric element 6 can have a certain thickness D6. However, in this specification, "certain thickness" does not necessarily mean that the thickness is strictly fixed; some variation is allowed within a range that does not significantly affect the characteristics of the elastic wave propagating in the piezoelectric element 6.

[0048] <Details of IDT Electrodes and Reflectors>

[0049] The IDT electrode 8 includes a pair of comb electrodes 10. In addition, in this specification, in the top view of the surface acoustic wave resonator 4 including Figure 1 in order to improve visibility, one of the comb electrodes 10 is marked with hatching. The comb electrode 10 includes, for example: a bus bar 12; a plurality of electrode fingers 14 extending from the bus bar 12; and a plurality of dummy electrodes 16 located between each of the plurality of electrode fingers 14 and protruding from the bus bar 12. Among the pair of comb electrodes 10, the plurality of electrode fingers 14 are configured to mesh with each other.

[0050] The bus bar 12 has a substantially constant width and is formed substantially along the propagation direction TD. In addition, the pair of bus bars 12 are opposed to each other in a direction substantially orthogonal to the propagation direction TD. Further, the bus bar 12 may have a width variation or may be formed inclined with respect to the propagation direction TD without significantly affecting the surface acoustic wave propagating through the piezoelectric body 6.

[0051] Each electrode finger 14 is formed in a strip shape substantially along the width direction of the bus bar 12. In each comb electrode 10, the electrode fingers 14 are arranged in the propagation direction TD. In addition, the electrode fingers 14 extending from one bus bar 12 and the electrode fingers 14 extending from the other bus bar 12 are alternately arranged in the propagation direction TD.

[0052] The number of each electrode finger 14 is not limited to Figure 1 the number shown and can be appropriately designed according to the characteristics required for the surface acoustic wave resonator 4. In addition, as Figure 1 shown, the length of each electrode finger 14 may be substantially constant, or may be different from each other according to the position in the propagation direction TD, and is implemented as so-called apodization. In addition, in a part of the IDT electrode 8, a part of the electrode finger 14 may also be "removed". In other words, the IDT electrode 8 may include a region where a part of the electrode finger 14 is not formed in the region where the IDT electrode 8 is formed.

[0053] Each dummy electrode 16 protrudes substantially along the width direction of the bus bar 12. In addition, the dummy electrode 16 protruding from one bus bar 12 is opposed to the front end of the electrode finger 14 extending from the other bus bar 12 with a gap in a direction orthogonal to the propagation direction TD. Further, the surface acoustic wave resonator 4 of the present embodiment may not include the dummy electrode 16.

[0054] The elastic wave resonator 4 further includes a pair of reflectors 18 located at both ends of the piezoelectric element 6 relative to the electrode fingers 14 in the propagation direction TD. Each reflector 18 includes a plurality of strip electrodes 22 extending from a pair of opposing busbars 20. The reflectors 18 can be electrically floating, or they can be given a reference potential. Furthermore, the IDT electrodes 8 and the reflectors 18 can be in the same layer or contained within a conductive layer. The IDT electrodes 8 and the reflectors 18 are formed of a metallic material, such as an alloy with Al as the main component. Additionally, the number, shape, etc., of the strip electrodes 22 of the reflectors 18 are not limited to... Figure 1 The structure shown can be designed appropriately, similar to electrode finger 14, according to the required characteristics of elastic wave resonator 4.

[0055] Additionally, in this specification, when referred to only as "electrode fingers," the "electrode fingers" include multiple electrode fingers 14 of the IDT electrode 8. Furthermore, when the elastic wave resonator 4 includes a reflector 18, the "electrode fingers" in this specification may also include multiple strip electrodes 22 of the reflector 18.

[0056] <Electrode finger spacing>

[0057] In the elastic wave resonator 4 of this embodiment, as follows: Figure 1 as well as Figure 2 As shown, the plurality of electrode fingers 14 of the IDT electrode 8 are located within the electrode finger arrangement region 24 when viewed from above. Furthermore, in this embodiment, the electrode finger arrangement region 24 includes at least a first region 24A and a second region 24B. Additionally, the electrode fingers 14 include a first electrode finger group 14A located in the first region 24A and a second electrode finger group 14B located in the second region 24B.

[0058] Specifically, in this embodiment, the electrode finger configuration area 24 may include at least one of a plurality of first areas 24A and second areas 24B. For example, as Figure 1 As shown, in the propagation direction TD, the electrode finger configuration region 24 symmetrically includes the first region 24A with respect to the second region 24B. In other words, the first region 24A is located at both ends of the second region 24B in the propagation direction TD.

[0059] Here, each of the plurality of electrode fingers 14 is arranged with a certain spacing between them. Furthermore, in the elastic wave propagating in the piezoelectric body 6, the resonant frequency of the elastic wave excited by the elastic wave resonator 4 depends on the spacing of the electrode fingers 14. Generally, the resonant frequency of the elastic wave excited by the elastic wave resonator 4 increases as the spacing of the electrode fingers 14 narrows.

[0060] Furthermore, in this specification, "resonant frequency" refers to the resonant frequency of the elastic wave excited by the main resonant mode in the elastic wave excited by the elastic wave resonator 4, and not the frequency of the elastic wave excited by the secondary resonant or stray mode.

[0061] In this embodiment, the first spacing PA of the first electrode finger group 14A is different from the second spacing PB of the second electrode finger group 14B. Specifically, for example, in this embodiment, the first spacing PA is shorter than the second spacing PB. For example, the first spacing PA is 0.708 μm and the second spacing PB is 0.745 μm.

[0062] Furthermore, although the thickness D6 of the piezoelectric element 6 is not particularly limited, in this embodiment, it is, for example, about 0.4 to 1.2 times that of either the first spacing PA or the second spacing PB. For example, the thickness D6 of the piezoelectric element 6 is about 0.28 μm to 0.9 μm.

[0063] Here, the thickness D6 of the piezoelectric element 6 is preferably less than or equal to the thickness of the first spacing PA in the first electrode finger group 14A or the second spacing PB in the second electrode finger group 14B. Thus, the resonant frequency can be increased by including the elastic wave resonator 4 with relatively wide spacing of the electrode fingers 14.

[0064] <Duty cycle of the electrode>

[0065] Here, the elastic wave resonator 4 of this embodiment has a resonant frequency action characteristic that acts in the direction of eliminating the effect of the difference in resonant frequency caused by the size relationship between the first spacing PA and the second spacing PB. In other words, in the elastic wave resonator 4 of this embodiment, due to the difference between the first spacing PA and the second spacing PB, the difference in resonant frequencies in the first region 24A and the second region 24B is smaller than the resonant frequency difference envisioned in conventional elastic wave resonators. Furthermore, in this specification, the resonant frequency action characteristic is sometimes simply referred to as the frequency action characteristic.

[0066] In this embodiment, the resonant frequency characteristic is the difference in duty cycles between the electrode fingers 14 in the first region 24A and the second region 24B. The duty cycle of an electrode finger 14 is the value obtained by dividing the width of a certain electrode finger 14 by the distance between that electrode finger 14 and its adjacent electrode fingers 14. Generally, the resonant frequency of the elastic wave excited by the elastic wave resonator 4 increases as the duty cycle of the electrode fingers 14 decreases.

[0067] In this embodiment, the duty cycle of the first electrode finger group 14A is different from that of the second electrode finger group 14B. Specifically, in this embodiment, the duty cycle of the first electrode finger group 14A is greater than that of the second electrode finger group 14B. Therefore, the difference in the duty cycles of the first electrode finger group 14A and the second electrode finger group 14B plays a role in eliminating the difference in resonant frequencies in the first region 24A and the second region 24B caused by the first pitch PA being shorter than the second pitch PB.

[0068] The duty cycles of the first electrode finger group 14A and the second electrode finger group 14B can be appropriately designed, such as... Figure 2 The design incorporates the first width WA of the electrode fingers 14 included in the first electrode finger group 14A and the second width WB of the electrode fingers 14 included in the second electrode finger group 14B.

[0069] For example, the duty cycle of the first electrode finger group 14A is 0.6, and the duty cycle of the second electrode finger group 14B is 0.3. As described above, when the first pitch PA is 0.708 μm and the second pitch PB is 0.745 μm, for example, the first width WA is about 0.4248 μm and the second width WB is 0.2235 μm.

[0070] Furthermore, in this embodiment, the thickness D14 of the electrode finger 14 can be the same in both the first region 24A and the second region 24B. For example, the thickness D14 of the electrode finger 14 is approximately 0.16 times that of either the first pitch PA or the second pitch PB. Additionally, the thickness of the strip electrode 22 of the reflector 18 can also be the same as the thickness of the electrode finger 14.

[0071] <Fixed base plate>

[0072] Returning to the description of each structure of the elastic wave resonator 4, as follows: Figure 2 As shown, the elastic wave resonator 4 also includes a support substrate 26, which is located further away from the IDT electrode 8 than the piezoelectric body 6. In this embodiment, the support substrate 26 has a sufficiently small impact on the characteristics of the elastic wave propagating through the piezoelectric body 6. Therefore, the material and dimensions of the support substrate 26 can be appropriately designed. For example, the support substrate 26 may include an insulating material and may include resin or ceramic. The thickness of the support substrate 26 is, for example, greater than the thickness D6 of the piezoelectric body 6. To further reduce the effect of temperature changes on the elastic wave characteristics, the coefficient of linear expansion of the material of the support substrate 26 is preferably lower than that of the piezoelectric body 6.

[0073] Furthermore, the elastic wave resonator 4 includes a reflective multilayer film 30 between the piezoelectric body 6 and the supporting substrate 26. The elastic wave resonator 4 may also include a sealing layer 28 between the reflective multilayer film 30 and the supporting substrate 26. In addition, the laminate including the piezoelectric body 6, the supporting substrate 26, the sealing layer 28, and the reflective multilayer film 30 is sometimes referred to as the fixed substrate 36.

[0074] The sealing layer 28 is inserted to improve the adhesion between the support substrate 26 and the reflective multilayer film 30, and has a sufficiently small effect on the elastic wave characteristics propagating in the piezoelectric material 6.

[0075] The reflective multilayer film 30 includes an alternately stacked first layer 32 and a second layer 34. The material of the first layer 32 has a lower acoustic impedance compared to the material of the second layer 34. As a result, the reflectivity of elastic waves is increased at the interface between the first layer 32 and the second layer 34, thus reducing the leakage of elastic waves propagating through the piezoelectric element 6 to the outside of the elastic wave filter.

[0076] For example, the first layer 32 is formed of silicon dioxide (SiO2). Alternatively, for example, the second layer 34 is formed of hafnium oxide (HfO2). Furthermore, the second layer 34 can also be formed of any one of tantalum pentoxide (Ta2O5), zirconium oxide (ZrO2), titanium oxide (TiO2), and magnesium oxide (MgO).

[0077] The reflective multilayer film 30 may include at least one first layer 32 and one second layer 34, and the number of layers is not particularly limited. Furthermore, the total number of the first layer 32 and the second layer 34 can be either odd or even. Here, although the layer in contact with the piezoelectric element 6 is the first layer 32, the layer in contact with the sealing layer 28 can be either the first layer 32 or the second layer 34.

[0078] For example, the reflective multilayer film 30 may include a first layer 32 and a second layer 34, which together comprise 3 to 12 layers. However, the reflective multilayer film 30 may consist of only a single first layer 32 and a single second layer 34. Furthermore, from the viewpoint of improving the adhesion between the layers of the reflective multilayer film 30 and preventing the diffusion of elastic waves in the reflective multilayer film 30, an adhesive layer 28 may be formed between each of the first layer 32 and the second layer 34.

[0079] In addition, such as Figure 2 As shown, the first layer 32 can have a certain thickness D32, and the second layer 34 can have a certain thickness D34. The thicknesses D32 and D34 can, for example, be about 0.25 times to 2 times that of either the first pitch PA or the second pitch PB.

[0080] <Uniformation of resonant frequency>

[0081] In this embodiment, for example, the resonant frequency of the main resonance of the elastic wave propagating through the piezoelectric element 6 in the first region 24A is the same as the resonant frequency of the main resonance of the elastic wave propagating through the piezoelectric element 6 in the second region 24B. Therefore, the frequency of the elastic wave excited in the piezoelectric element 6 is homogenized in the first region 24A and the second region 24B, improving the characteristics of the elastic wave resonator 4.

[0082] Furthermore, in this specification, "same frequency" does not necessarily mean that the frequencies are strictly the same. For example, within a range that does not significantly affect the characteristics of the elastic wave resonator 4, some differences are allowed in the resonant frequencies of the main resonances of the elastic waves propagating through the piezoelectric element 6 in the first region 24A and the second region 24B.

[0083] Specifically, in determining whether the resonant frequencies in the first region 24A and the second region 24B are the same, the value obtained by dividing the difference between the resonant frequencies in the first region 24A and the second region 24B by the desired resonant frequency and multiplying it by 100 (dfr) can also be used. For example, if dfr is between -0.856 and 0.856, it can also be considered that the resonant frequencies in the first region 24A and the second region 24B are the same.

[0084] When the value of dfr meets the above range, the generation of spurious signals caused by the elastic wave resonator 4 including the first region 24A and the second region 24B in its frequency characteristics can be suppressed. Furthermore, in this embodiment, when the above range is met, the absolute value of the difference between the resonant frequencies in the first region 24A and the second region 24B is 50 MHz or less.

[0085] Furthermore, when dfr is -1.028 or 1.028, spurious emissions are confirmed. In this case, in this embodiment, the absolute value of the difference between the resonant frequencies in the first region 24A and the second region 24B is equivalent to 60 MHz.

[0086] Reference Figure 3 The method for homogenizing the resonant frequencies in the first region 24A and the second region 24B is described in more detail. Figure 3 This is a graph showing the extent to which the duty cycle changes relative to the spacing when the resonant frequency of the excited elastic wave is constant in an elastic wave resonator with the same structure as the elastic wave resonator 4 in this embodiment.

[0087] exist Figure 3In the diagram, the solid line represents the simulated value indicating how the duty cycle changes relative to the spacing, and the dashed line represents an approximation of the spacing and duty cycle based on that simulated value. The approximation can be chosen to best suit the simulated value. For example, a power approximation, logarithmic approximation, or polynomial approximation can be appropriately selected. Furthermore, in the example above, since the approximation based on the power approximation provides the most accurate approximation, the power approximation was used to obtain the approximation. Figure 3 In the graph, the vertical axis represents the spacing (unit: μm), and the horizontal axis represents the duty cycle.

[0088] Let the spacing be y (unit: μm) and the duty cycle be x. Then, given a constant resonant frequency of the excited elastic wave, the relationship between the spacing and the duty cycle can be approximated as y = 0.6823x^(-0.073). Furthermore, the sum of the squared errors between the above simulated value and the approximation, R², is 0.9987.

[0089] like Figure 3 As shown in the figure, when the resonant frequency of the excited elastic wave is constant, the relationship between the duty cycle and the change in spacing can be calculated. Therefore, in this embodiment, the duty cycle of the first electrode finger group 14A and the duty cycle of the second electrode finger group 14B, which are used to make the resonant frequencies in the first region 24A and the second region 24B the same, can be calculated based on the first spacing PA and the second spacing PB.

[0090] <Characteristic changes caused by differences in spacing and duty cycle>

[0091] Figure 4 This is a graph showing the characteristics of the excited elastic wave in an elastic wave resonator having the same structure as the elastic wave resonator 4 in this embodiment, and a graph showing the phase of the impedance in the elastic wave resonator at each frequency. In other words, Figure 4 The graph represents the intensity of the elastic wave oscillating in the elastic wave resonator at each frequency. Figure 4 In the graph, the vertical axis represents phase (unit: degrees), and the horizontal axis represents frequency (unit: MHz).

[0092] exist Figure 4 In the diagram, the solid line represents the simulation results obtained in an elastic wave resonator with the duty cycle of electrode finger 14 set to 0.6. Additionally, in Figure 4 In the diagram, the dashed line represents the simulation results obtained in an elastic wave resonator with the duty cycle of electrode finger 14 set to 0.3. Furthermore, in Figure 4 The distance between the electrode fingers 14 of the two simulated elastic wave resonators in the figure is based on... Figure 3 The relationship shown was determined to make the resonant frequencies the same. Figure 4In the diagram, Figure 402 is a magnified view of the phase of Figure 401 from -90 degrees to -80 degrees.

[0093] from Figure 4 As shown in the figure, even between two elastic wave resonators with different spacing and duty cycles, the resonant frequency with the highest impedance phase remains almost unchanged. Furthermore, by confirming the absolute values ​​of the impedance between two elastic wave resonators with different spacing and duty cycles, the resonant frequency and anti-resonant frequency were also confirmed. This confirms that even in this case, the resonant frequency and anti-resonant frequency between two elastic wave resonators with different spacing and duty cycles remain almost unchanged.

[0094] However, as Figure 4 As clearly shown in Figure 402, the frequencies of the spurious waves excited at frequencies other than the resonant frequency differ between the two elastic wave resonators described above. These elastic waves excited at frequencies other than the resonant frequency include the frequencies excited in the spurious mode.

[0095] Figure 5 This is a graph showing the frequencies of the elastic wave excited by an elastic wave resonator having the same structure as the elastic wave resonator 4 in this embodiment, when the spacing and duty cycle are changed to keep the resonant frequency constant. Figure 5 In the graph, the horizontal axis represents the spacing (unit: μm) and duty cycle, and the vertical axis represents the frequency (unit: MHz). Here, in... Figure 5 In the figure, the value of the electrode finger spacing changes with the duty cycle, according to Figure 3 The relationship shown has changed.

[0096] exist Figure 5 In the figure, the white circles represent the calculated frequencies of the elastic waves excited in the main resonance and anti-resonance modes by the elastic wave resonator, obtained through simulation. Figure 5 In the figure, the black circles indicate the calculated results obtained by simulation of the stray frequencies excited in modes other than the main resonance and anti-resonance modes by the elastic wave resonator.

[0097] like Figure 5 As shown on the horizontal axis, by changing the duty cycle and spacing of the electrode fingers, the frequencies of the elastic waves excited in the main resonance and anti-resonance modes of the elastic wave resonator are kept approximately constant. Here, in Figure 5 As an example, an elastic wave resonator with the following characteristics is listed: it has a primary resonant frequency around 5350MHz and an anti-resonant frequency around 5500MHz.

[0098] However, as Figure 5As shown, the frequency of the elastic wave excited in stray mode changes with the duty cycle and spacing of the electrode fingers. This is because the frequency of the elastic wave excited in stray mode has a different dependence on the duty cycle and spacing of the electrode fingers compared to the frequency of the elastic wave excited in main resonance and anti-resonance modes.

[0099] <Effects of the Elastic Wave Resonator in Implementation Method 1>

[0100] The elastic wave resonator 4 of this embodiment includes, within the same resonator, a first electrode finger group 14A and a second electrode finger group 14B with different spacings. Furthermore, the elastic wave resonator 4 has a resonant frequency characteristic that eliminates the effect of the difference in the spacing between the first electrode finger group 14A and the second electrode finger group 14B on the high and low resonant frequencies. In this embodiment, the resonant frequency characteristic is the difference in the duty cycles of the first electrode finger group 14A and the second electrode finger group 14B. In other words, due to the difference in the duty cycles of the first electrode finger group 14A and the second electrode finger group 14B, the difference in the resonant frequencies caused by the difference in the spacing between the first electrode finger group 14A and the second electrode finger group 14B is reduced.

[0101] Therefore, the elastic wave resonator 4 includes a first electrode finger group 14A and a second electrode finger group 14B with different spacing and duty cycles and smaller differences in resonant frequencies. Thus, between the first region 24A and the second region 24B, the frequency uniformity of the elastic wave excited in the main resonant mode can be further maintained, and the frequencies of the elastic waves excited in the spurious mode can be made more distinct. Therefore, according to this embodiment, within the same elastic wave resonator 4, by maintaining the uniformity of the resonant frequency and dispersing the frequencies of the elastic waves excited in the spurious mode, the intensity of spurious waves can be reduced.

[0102] In particular, from the viewpoint of improving the characteristics of the elastic wave excited in the elastic wave resonator 4, in this embodiment, the frequency of the elastic wave excited in the main resonance mode is preferably the same between the first region 24A and the second region 24B. In this case, the resonant frequency in more than 80% of the region where the electrode finger 14 is located is preferably the same as the resonant frequency of the elastic wave in the first region 24A and the second region 24B. As a result, the characteristics of the elastic wave excited in the elastic wave resonator 4 can be further improved. Here, the region where the electrode finger 14 is located refers to the region in the electrode finger arrangement region 24 where the electrode finger 14 is formed when viewed from above.

[0103] Furthermore, in this embodiment, regions with the same and different frequencies of the elastic waves excited in the main resonant mode can be mixed together between the first region 24A and the second region 24B. For example, the first region 24A may include electrode fingers 14 located at the end on one side of the reflector 18, designed as irregular electrode fingers to adjust the characteristics of the elastic wave resonator 4. Additionally, in both the first region 24A and the second region 24B, the IDT electrode 8 may include regions with discontinuous electrode fingers designed in the propagation direction TD.

[0104] In this embodiment, the electrode finger configuration region 24 symmetrically includes the first region 24A with respect to the second region 24B in the propagation direction TD. Therefore, the spacing and duty cycle of the electrode fingers 14 of the elastic wave resonator 4 can be symmetrically designed in the propagation direction TD. Therefore, in this embodiment, the characteristics of the elastic wave excited in the elastic wave resonator 4 can be further improved.

[0105] Furthermore, in the elastic wave resonator 4 of this embodiment, the electrode finger arrangement region 24 may also include a second region 24B symmetrically with respect to the first region 24A in the propagation direction TD. In other words, the elastic wave resonator 4 of this embodiment may include the other of the first region 24A and the second region 24B symmetrically with respect to one of the first region 24A and the second region 24B in the propagation direction TD.

[0106] Furthermore, in this embodiment and the various embodiments described below, the behavior of the resonant frequency in each elastic wave resonator is described as an example. Here, generally, the resonant frequency and anti-resonant frequency of the elastic wave resonator exhibit similar behavior with respect to changes in spacing or duty cycle. Therefore, in various embodiments where the behavior of the resonant frequency is described as an example, the resonant frequency can be replaced with the anti-resonant frequency. In other words, the elastic wave resonator 4 can also have a frequency response characteristic that eliminates the effect of the difference in spacing between the first electrode finger group 14A and the second electrode finger group 14B on the high and low anti-resonant frequencies.

[0107] [Implementation Method Two]

[0108] <Middle Area>

[0109] Figure 6 This is a schematic top view of the elastic wave resonator 4A in this embodiment. Figure 7 This is a schematic cross-sectional view of the elastic wave resonator 4A in this embodiment, along... Figure 6 A sectional view along line BB. Furthermore, in this specification, components with the same function are given the same names and reference numerals, and identical descriptions are not repeated unless there are structural differences.

[0110] like Figure 6 as well as Figure 7 As shown, the electrode finger arrangement region 24 of the elastic wave resonator 4A in this embodiment further includes an intermediate region 24C, which, when viewed from above, differs from the first region 24A and the second region 24B. Specifically, in the propagation direction TD, the electrode finger arrangement region 24 of the elastic wave resonator 4A in this embodiment symmetrically includes the first region 24A with respect to the second region 24B, and includes intermediate regions 24C between the first region 24A and the second region 24B, respectively.

[0111] Electrode fingers 14 further include an intermediate electrode finger group 14C, which is different from the first electrode finger group 14A and the second electrode finger group 14B and is located in the intermediate region 24C. In addition, the intermediate spacing PC of the intermediate electrode finger group 14C is the value between the first spacing PA of the first electrode finger group 14A and the second spacing PB of the second electrode finger group 14B.

[0112] Furthermore, the resonant frequency of the main resonance of the intermediate electrode finger group 14C is a value between the resonant frequencies of the main resonances of the first electrode finger group 14A and the second electrode finger group 14B. In this embodiment, by using the spacing of the intermediate electrode finger group 14C... Figure 3 The duty cycle of the intermediate electrode finger group 14C can be appropriately designed using the relationship shown, thereby allowing the design of the resonant frequency of the main resonance of the intermediate electrode finger group 14C. Furthermore, when the resonant frequencies of the main resonances of the first electrode finger group 14A and the second electrode finger group 14B are the same, the resonant frequency of the main resonance of the intermediate electrode finger group 14C is also the same as the resonant frequencies of the main resonances of the first electrode finger group 14A and the second electrode finger group 14B.

[0113] In this embodiment, for example, the intermediate spacing PC of each intermediate electrode finger group 14C gradually changes from the first region 24A side to the second region 24B side. Specifically, for example, when the first spacing PA is 0.708 μm and the second spacing PB is 0.745 μm, the intermediate spacing PC monotonically increases from 0.708 μm to 0.745 μm from the first region 24A side to the second region 24B side.

[0114] As the spacing PC of the intermediate electrode finger group 14C gradually changes from the first region 24A side to the second region 24B side, the duty cycle of the intermediate electrode finger group 14C also gradually changes from the first region 24A side to the second region 24B side. Specifically, in the above example, the duty cycle of the intermediate electrode finger group 14C monotonically decreases from 0.6 to 0.3 from the first region 24A side to the second region 24B side. Here, the duty cycle at each position of the intermediate electrode finger group 14C is designed such that the resonant frequency of the main resonance of the intermediate electrode finger group 14C is between the resonant frequencies of the main resonances of the first electrode finger group 14A and the second electrode finger group 14B at any position.

[0115] <Effects of the Elastic Wave Resonator in Implementation Method Two>

[0116] The elastic wave resonator 4A in this embodiment further includes, within the same resonator, an intermediate electrode finger group 14C with a spacing different from that of the first electrode finger group 14A and the second electrode finger group 14B. Furthermore, the resonant frequency of the main resonance of the elastic wave in the intermediate region 24C where the intermediate electrode finger group 14C is located is a value between the resonant frequencies of the main resonances of the elastic waves in the first region 24A and the second region 24B.

[0117] Therefore, the frequency uniformity of the elastic wave excited in the main resonance mode can be further maintained between the first electrode finger group 14A, the second electrode finger group 14B, and the intermediate electrode finger group 14C, and the frequency of the elastic wave excited in the spurious mode can be further differentiated. Thus, according to this embodiment, within the same elastic wave resonator 4A, the uniformity of the resonant frequency can be maintained while the intensity of spurious waves is further reduced.

[0118] Furthermore, in this embodiment, the spacing and duty cycle within the intermediate region 24C are different at various locations within the intermediate region 24C. Therefore, the frequency of the elastic wave excited in spurious mode can also be different at various locations within the intermediate region 24C. Thus, according to this embodiment, within the same elastic wave resonator 4A, while maintaining the uniformity of the resonant frequency, the intensity of spurious waves is further reduced.

[0119] Furthermore, in this embodiment, the spacing and duty cycle within the intermediate region 24C gradually change within the intermediate region 24C. This prevents significant changes in the spacing and duty cycle configuration at each position within the elastic wave resonator 4A. Therefore, in this embodiment, the characteristics of the elastic wave excited in the elastic wave resonator 4A can be further improved.

[0120] Furthermore, each of the electrode fingers 14 constituting the first region 24A and the second region 24B requires at least two fingers. In this case, the spacing and duty cycle of the electrode fingers 14 within all electrode finger arrangement areas 24, including the intermediate region 24C, change slowly.

[0121] <Comparison of characteristics between the examples and comparative examples>

[0122] Through simulation, the characteristics of elastic wave resonators in Embodiments 1, 2, and 3, which have structures corresponding to the elastic wave resonator 4A of this embodiment, were calculated.

[0123] Regarding the elastic wave resonator of Embodiment 1, except for the values ​​exemplified in Embodiment 1, the dimensions and other parameters of each component are set as follows. The IDT electrode 8 and the reflector 18 use Al with a thickness of 0.13 μm. The electrode finger arrangement region 24 is the same as the electrode finger arrangement region 24 of this embodiment, and in the propagation direction TD, it includes a first region 24A symmetrically with respect to the second region 24B, and includes intermediate regions 24C between the first region 24A and the second region 24B. The duty cycle of the electrode finger 14 of the IDT electrode 8 is set to monotonically increase from 0.3 to 0.6 in the first region 24A, intermediate region 24C, and second region 24B. In addition, the fixed substrate 36 of the elastic wave resonator of Embodiment 1 has a reflective multilayer film 30 formed by alternatingly stacking a first layer 32 and a second layer 34 (a total of 8 layers) on a Si support substrate 26, and a piezoelectric element 6 is formed thereon. The first layer 32 is formed of SiO2 with a thickness of 0.2 μm, and the second layer 34 is formed of HfO2 with a thickness of 0.17 μm. The thickness D6 of the piezoelectric body 6 is 0.415 μm. Furthermore, the piezoelectric body 6 is an LT crystal with a Y-cut angle and X-propagation of 114°.

[0124] Regarding the elastic wave resonator of Embodiment 2, the dimensions and other parameters of each component are set as follows. The IDT electrode 8 and reflector 18 use Al with a thickness of 0.18 μm. The electrode finger arrangement region 24 is the same as that in this embodiment, symmetrically including a first region 24A relative to the second region 24B in the propagation direction TD, and including intermediate regions 24C between the first region 24A and the second region 24B. The duty cycle of the electrode fingers 14 of the IDT electrode 8 is set to monotonically increase from 0.3 to 0.6 in the first region 24A, intermediate region 24C, and second region 24B. The spacing of the electrode fingers 14 is set to 1 μm at a duty cycle of 0.5; and the spacing of the electrode fingers 14 at each position is varied so that the resonant frequency is constant at any position within the electrode finger arrangement region 24. In addition, the fixed substrate 36 of the elastic wave resonator in Embodiment 2 is configured such that a piezoelectric body 6 is directly formed on the support substrate 26 of Si, and the thickness D6 of the piezoelectric body 6 is 24 μm.

[0125] Regarding the elastic wave resonator of Embodiment 3, the dimensions and other parameters of each component are set as follows. The IDT electrode 8 and reflector 18 use Al with a thickness of 0.135 μm. The electrode finger arrangement region 24 is the same as that in this embodiment, symmetrically including a first region 24A relative to the second region 24B in the propagation direction TD, and including intermediate regions 24C between the first region 24A and the second region 24B. The duty cycle of the electrode fingers 14 of the IDT electrode 8 is set to monotonically increase from 0.3 to 0.6 in the first region 24A, intermediate region 24C, and second region 24B. The spacing of the electrode fingers 14 is set to 0.751 μm at a duty cycle of 0.5; and the spacing of the electrode fingers 14 at each position is varied so that the resonant frequency is constant at any position within the electrode finger arrangement region 24. In addition, the fixed substrate 36 of the elastic wave resonator in Embodiment 3 is configured such that a piezoelectric body 6 is directly formed on the support substrate 26 of Si, and the thickness D6 of the piezoelectric body 6 is 2.2 μm.

[0126] In addition, as a comparison object with the elastic wave resonators of each of Embodiments 1, 2 and 3, the characteristics of the elastic wave resonators of each of Comparative Example 1, Comparative Example 2 and Comparative Example 3 were also calculated by simulation.

[0127] The elastic wave resonator of Comparative Example 1 differs from that of Example 1 only in that the duty cycle of the electrode fingers 14 is 0.6 and the spacing is 0.708 at any position within the electrode finger arrangement region 24. The elastic wave resonator of Comparative Example 2 differs from that of Example 2 only in that the duty cycle of the electrode fingers 14 is 0.6 and the spacing is 0.995 μm at any position within the electrode finger arrangement region 24. The elastic wave resonator of Comparative Example 3 differs from that of Example 3 only in that the duty cycle of the electrode fingers 14 is 0.6 and the spacing is 0.748 μm at any position within the electrode finger arrangement region 24.

[0128] Figure 8 , Figure 9 This is a graph showing the characteristics of the elastic waves excited in the elastic wave resonators of each embodiment and comparative example, and a graph showing the impedance phase in the elastic wave resonator at each frequency. Figure 8 , Figure 9 In the graph, the vertical axis represents phase (unit: degrees), and the horizontal axis represents frequency (unit: MHz). Figure 8 In the figure, the characteristics of the elastic wave resonator of Example 1 are represented by solid lines, and the characteristics of the elastic wave resonator of Comparative Example 1 are represented by dashed lines. Figure 9 Figure 901 shows the characteristics of the elastic wave resonator of Example 2 with solid lines and the characteristics of the elastic wave resonator of Comparative Example 2 with dashed lines. Figure 9 Figure 902 shows the characteristics of the elastic wave resonator of Example 3 with solid lines and the characteristics of the elastic wave resonator of Comparative Example 3 with dashed lines.

[0129] from Figure 8 The figures also show that for the elastic wave resonators of Example 1 and Comparative Example 1, the resonant frequency and intensity of the elastic wave oscillating in the main resonance mode at a frequency of around 5800MHz to 5900MHz are approximately the same. However, compared to Comparative Example 1, the intensity of the elastic wave oscillating in the stray mode at a frequency above 5900MHz of the elastic wave resonator of Example 1 is reduced.

[0130] from Figure 9 As can be seen from Figure 901, the resonant frequencies and intensities of the elastic waves oscillating in the main resonance mode at frequencies around 1900MHz to 2000MHz in the elastic wave resonators of Example 2 and Comparative Example 2 are approximately the same. However, compared to Comparative Example 2, the intensity of the elastic waves oscillating in the spurious mode at frequencies above 2200MHz in the elastic wave resonator of Example 2 is reduced.

[0131] from Figure 9As can be seen from Figure 902, the resonant frequency and intensity of the elastic waves oscillating in the main resonance mode at frequencies around 2600MHz to 2700MHz are approximately the same for the elastic wave resonators of Example 3 and Comparative Example 3. However, compared to Comparative Example 3, the intensity of the elastic waves oscillating in the spurious mode at frequencies above 2800MHz of the elastic wave resonator of Example 3 is reduced.

[0132] Therefore, compared with elastic wave resonators with a fixed spacing of electrode fingers 14 and a fixed duty cycle, the elastic wave resonators of each embodiment can maintain the intensity of elastic waves oscillating in the main resonance mode and reduce the intensity of elastic waves oscillating in the stray mode.

[0133] <Maximum duty cycle value and its relationship with characteristics>

[0134] In the elastic wave resonator 4A of this embodiment, by changing the maximum and minimum values ​​of the duty cycle of the electrode fingers 14, the characteristics of each elastic wave resonator 4A are calculated through simulation. Figure 10 As shown in the diagram. Furthermore, in Figure 10 The elastic wave resonators 4A shown in the figure have the same structure as in Example 1, except for the maximum and minimum duty cycles of the electrode fingers 14. The simulation was performed.

[0135] Figure 10 The figures in this embodiment show the maximum phase of the impedance of each elastic wave resonator 4A when the maximum and minimum values ​​of the duty cycle of the electrode fingers 14 are changed.

[0136] Figure 10 Figure 1001 is a diagram showing the maximum phase of the impedance at the frequency of the elastic wave oscillating in the main resonant mode of each elastic wave resonator 4A. In other words, Figure 10 Figure 1001 is a graph showing the maximum intensity of the elastic wave oscillating in the main resonant mode of each elastic wave resonator 4A.

[0137] Figure 10 Figure 1002 is a graph showing the maximum phase of the impedance at the frequency of the elastic wave oscillating in the spurious modes of each elastic wave resonator 4A. Here, Figure 1002 shows the frequency with the maximum phase of the impedance among all the frequencies of the elastic wave oscillating in the spurious modes. In other words, Figure 10 Figure 1002 is a graph showing the maximum intensity of the elastic wave oscillating in the stray mode of each elastic wave resonator 4A.

[0138] exist Figure 10In each figure, the vertical axis represents the phase (unit: deg), and the horizontal axis represents the absolute value of the product of the maximum and minimum duty cycles of electrode finger 14 minus 0.61.

[0139] The maximum duty cycle was changed from 0.6 to 0.35, and the minimum duty cycle was changed from 0.5 to 0.3, in increments of 0.05. Each maximum phase was calculated through simulation, and the results were plotted. Figure 10 In each of the diagrams. Figure 10 The thin lines in each diagram connect points with the same maximum duty cycle. Additionally, Figure 10 The thick lines in each of the diagrams connect points with the same minimum duty cycle.

[0140] from Figure 10 As shown in Figure 1001, the smaller the difference between the maximum and minimum duty cycle values, the greater the tendency for the maximum intensity of the elastic wave oscillating in the main resonance mode to increase. Conversely, the larger the maximum and minimum duty cycle values, the greater the tendency for the maximum intensity of the elastic wave oscillating in the main resonance mode to increase.

[0141] from Figure 10 As shown in Figure 1002, the greater the difference between the maximum and minimum duty cycles, the more likely the maximum intensity of the elastic wave oscillating in stray mode is to decrease. Furthermore, although the greater the minimum duty cycle, the more likely the maximum intensity of the elastic wave oscillating in stray mode is to decrease, there is a minimum tendency when the maximum duty cycle is 0.55.

[0142] As described above, for the elastic wave resonator 4A of this embodiment, to ensure a high maximum intensity of the elastic wave oscillating in the main resonance mode, the difference between the maximum and minimum values ​​of the duty cycle of the electrode finger 14 can be reduced. Conversely, for the elastic wave resonator 4A of this embodiment, to control the maximum intensity of the elastic wave oscillating in the stray mode to a low level, the difference between the maximum and minimum values ​​of the duty cycle of the electrode finger 14 can be increased. The design of these maximum and minimum duty cycle values ​​can also be appropriately determined by considering factors such as the intended use of the elastic wave resonator 4A. Furthermore, the aforementioned tendencies of the elastic wave resonator 4A are independent of the value of the duty cycle of the strip electrode 22 of the reflector 18.

[0143] <Changes in the spacing between intermediate areas>

[0144] Figure 11 This is a diagram showing the relationship between the position of the electrode index 14 of the elastic wave resonator 4A in the propagation direction TD and the duty cycle. Figure 11In the diagram, the horizontal axis represents the position of the electrode finger 14 formed on the elastic wave resonator 4A in the propagation direction TD, and the vertical axis represents the duty cycle of the electrode finger 14 at that position. The horizontal axis shows 24A, 24B, and 24C, which correspond to the positions forming the first region 24A, the second region 24B, and the intermediate region 24C, respectively.

[0145] In this embodiment, as shown in FIG1101, the duty cycle of the electrode finger 14 formed in the intermediate region 24C can vary linearly from the first region 24A to the second region 24B. Alternatively, in this embodiment, as shown in FIG1102, the duty cycle of the electrode finger 14 formed in the intermediate region 24C can vary non-linearly from the first region 24A to the second region 24B. In other words, the amount of change in the duty cycle of the electrode finger 14 formed in the intermediate region 24C can gradually change from the first region 24A to the second region 24B.

[0146] Furthermore, since the duty cycle of each electrode finger is determined by each individual electrode finger, therefore, originally Figure 11 The graph should be plotted discretely for the duty cycle values. However, in this specification, when the change in the duty cycle of electrode finger 14 is represented graphically, for the sake of simplicity, the duty cycle of electrode finger 14 is plotted as a continuous change.

[0147] [Variation Example]

[0148] <First Intermediate Region and Second Intermediate Region>

[0149] Figure 12 This is a schematic top view of the elastic wave resonator 4F, a modified example of this embodiment. Figure 12 As shown, the intermediate region 24C of the elastic wave resonator 4F includes a first intermediate region 24D and a second intermediate region 24E. Additionally, the intermediate electrode finger group 14C includes a first intermediate electrode finger group 14D formed in the first intermediate region 24D and a second intermediate electrode finger group 14E formed in the second intermediate region 24E.

[0150] The first intermediate spacing PD of the first intermediate electrode finger group 14D gradually changes from the first region 24A side to the second region 24B side based on a first variation amount. On the other hand, the spacing of the second intermediate electrode finger group 14E gradually changes from the first region 24A side to the second region 24B side based on a second variation amount different from the first variation amount.

[0151] Here, the first change and the second change can differ depending on their positions in the first intermediate region 24D and the second intermediate region 24E, respectively. Furthermore, the first change differing from the second change means, for example, that the maximum value of the first change is smaller than the minimum value of the second change, or that the minimum value of the first change is larger than the maximum value of the second change.

[0152] Furthermore, the resonant frequencies of the primary resonant frequencies of the first intermediate electrode finger group 14D and the second intermediate electrode finger group 14E are between the resonant frequencies of the primary resonant frequencies of the first electrode finger group 14A and the second electrode finger group 14B. In addition, the duty cycles of the first intermediate electrode finger group 14D and the second intermediate electrode finger group 14E also gradually change from the first region 24A side to the second region 24B side.

[0153] Figure 13 This is a diagram showing the relationship between the position of electrode index 14 of the elastic wave resonator 4F in the propagation direction TD and the duty cycle in this modified example. Figure 13 In the diagram, the horizontal axis represents the position of the elastic wave resonator 4F with electrode fingers 14 in the propagation direction TD, and the vertical axis represents the duty cycle of the electrode fingers 14 at that position. The horizontal axis points 24A, 24B, 24D, and 24E, corresponding to the positions forming the first region 24A, the second region 24B, the first intermediate region 24D, and the second intermediate region 24E, respectively.

[0154] In this variation, the change in the first intermediate spacing PD is different from the change in the second intermediate spacing PE. Therefore, for example, as... Figure 13 As shown in Figure 1301, the change in duty cycle of the first electrode finger group 14D formed in the first intermediate region 24D and the change in duty cycle of the second electrode finger group 14E formed in the second intermediate region 24E are different from each other. Therefore, the change in duty cycle of the intermediate region 24C varies from the first region 24A to the second region 24B.

[0155] Furthermore, although the example given in this modified elastic wave resonator 4F is that a first intermediate region 24D and a second intermediate region 24E are formed in the intermediate region 24C, it is not limited to this. For example, the modified elastic wave resonator 4F may also have two second intermediate regions 24E formed in the intermediate region 24C, and a first intermediate region 24D formed between the two second intermediate regions 24E. In this case, as... Figure 13 As shown in Figure 1302, the duty cycle of the intermediate region 24C can change more than twice from the first region 24A to the second region 24B.

[0156] In this modified elastic wave resonator 4F, the duty cycle of the electrode fingers 14 in the intermediate region 24C can be gradually varied, and the amount of variation can be changed according to their position. Therefore, the elastic wave resonator 4F allows for the design of the duty cycle distribution of the electrode fingers 14 in the intermediate region 24C. For example, the elastic wave resonator 4F of this modified example can reduce the area of ​​the region where electrode fingers 14 with a duty cycle that is unfavorable for reducing spurious emissions. For example, the elastic wave resonator 4F can reduce the intensity of spurious emissions by increasing the amount of variation of the duty cycle of the electrode fingers 14 in the intermediate region 24C around the periphery of the duty cycle where the spurious emissions intensity becomes relatively strong.

[0157] <Spurious intensity dependence>

[0158] Typically, the intensity and frequency of stray emissions generated in an elastic wave resonator vary depending on factors such as the duty cycle of the electrode fingers, their spacing, or the thickness of the piezoelectric element. The following will refer to... Figures 14 to 17 The bubble diagram shown illustrates an example of the dependence of the intensity and frequency of stray energy generated in an elastic wave resonator.

[0159] Figures 14 to 17 This is a bubble diagram illustrating the intensity of the resonant wave generated in the elastic wave resonator of this embodiment and the comparative example. Figures 14 to 17 In their respective bubble diagrams, the horizontal axis represents the thickness of the piezoelectric element (unit: μm), and the vertical axis represents the frequency (unit: MHz). Figures 14 to 17 The size of the bubbles in each bubble diagram represents the intensity of the generated elastic wave.

[0160] Figures 14 to 17 The bubble diagram shows the intensity of the resonant wave generated in the elastic wave resonator when the duty cycles of the electrode fingers of the elastic wave resonator in this embodiment and the comparative example are set to 0.6, 0.5, 0.4 and 0.3, respectively.

[0161] Figure 14 The bubble diagram shows the characteristics at a main resonant frequency of 4250MHz. Figure 15 The bubble diagram shows the characteristics at a main resonant frequency of 4500MHz. Figure 16 The bubble diagram shows the characteristics at a main resonant frequency of 4700MHz. Figure 17 The bubble diagram illustrates the characteristics at a principal resonant frequency of 4900 MHz. Therefore, in Figures 14 to 17 The bubble diagram shows that the smaller the bubble is at locations other than the main resonant frequency, the weaker the intensity of the stray gas produced.

[0162] For example, in Figure 14 as well as Figure 15In the elastic wave resonator with characteristics shown, when the thickness of the elastic body is set to 0.44 μm, the intensity of stray waves can be reduced when the duty cycle is set to 0.3 or 0.4 compared to when the duty cycle is set to 0.5 or 0.6. On the other hand, in Figure 16 as well as Figure 17 In the elastic wave resonator with the characteristics shown, when the thickness of the elastic body is set to 0.44 μm, the intensity of stray waves can be reduced when the duty cycle is set to 0.5 or 0.6 compared to when the duty cycle is set to 0.3 or 0.4.

[0163] Thus, as Figures 14 to 17 As shown in the bubble diagram, by simulating the dependence of the intensity of spurs generated in the elastic wave resonator, the intensity of spurs can be reduced, and the duty cycle of each electrode finger can be calculated.

[0164] The elastic wave resonator 4F in this modified example can, for example, be based on... Figures 14 to 17 The bubble diagram shown illustrates the characteristics of the electrode index 14, where the stray intensity is relatively strong, calculated for each elastic wave resonator 4F. Existing known techniques can be used to appropriately calculate, for example... Figures 14 to 17 The bubble diagrams show the characteristics of the elastic wave resonator. Therefore, in the elastic wave resonator 4F, it is possible to calculate the region where the change in the duty cycle of the electrode finger 14 in the intermediate region 24C is increased.

[0165] <Characteristics of the modified elastic wave resonator>

[0166] Figure 18 This is a graph showing the characteristics of the excited elastic wave in an elastic wave resonator having the same structure as the elastic wave resonator 4A of this embodiment or the elastic wave resonator 4F of this modified example; it is a graph showing the phase of the impedance in the elastic wave resonator at each frequency. In other words, Figure 18 The graph represents the intensity of the elastic wave oscillating in the elastic wave resonator at each frequency. Figure 18 In the graph, the vertical axis represents phase (unit: degrees), and the horizontal axis represents frequency (unit: MHz).

[0167] Figure 18 Figure 1401 shows that in the elastic wave resonator 4A of this embodiment, the change in the duty cycle of the electrode finger 14 in the intermediate region 24C is set as Figure 11 Figure 1101 shows the characteristics of the elastic wave resonator when the duty cycle changes. Figure 18 Figure 1402 shows that in the modified elastic wave resonator 4F, the change in the duty cycle of the electrode finger 14 in the intermediate region 24C is set as Figure 13 Figure 1301 shows the characteristics of the elastic wave resonator when the duty cycle changes.

[0168] Compare Figure 18 Figures 1401 and 1402 show that, in Figure 1402, the intensity of spurious emissions near a frequency of 6000 MHz is reduced. This is because, compared to the elastic wave resonator 4A, the elastic wave resonator 4F has a smaller region of electrode fingers 14 with a duty cycle that strengthens the spurious emissions of electrode fingers 14 in the intermediate region 24C.

[0169] Figure 18 Figure 1403 shows the elastic wave resonator 4F in the modified example, from Figure 13 Figure 1301 shows the characteristics of the elastic wave resonator under different duty cycles of electrode finger 14 in the middle region 24C. (Comparison) Figure 18 Figures 1401 and 1403 show that the balance of spurious intensity changes near 5250 MHz and near 6000 MHz. Thus, in the elastic wave resonator 4F of this modified example, the balance of spurious intensity can be designed by adjusting the change in the duty cycle of the electrode finger 14 in the intermediate region 24C.

[0170] Figure 18 Figure 1404 shows the variation of the duty cycle of the electrode finger 14 in the intermediate region 24C in the modified elastic wave resonator 4F, where the variation is set as... Figure 13 Figure 1302 shows the characteristics of the elastic wave resonator. Figure 18 In Figure 1404, compared with Figure 1401, the intensity of spurious emissions near 5250 MHz and near 6000 MHz is reduced.

[0171] In the elastic wave resonator 4F of this modification, the region where the electrode fingers 14 with a duty cycle that increases spurious intensity can be formed can be reduced. Thus, the electrode fingers 14 can be more easily designed according to the elastic wave resonator 4F of this modification to further reduce the intensity of the generated spurious signals.

[0172] [Implementation Method 3]

[0173] <Differences in electrode thickness>

[0174] Figure 19 In the context of Figure 2 The diagram shows a schematic cross-sectional view of the elastic wave resonator 4B of this embodiment at the position corresponding to the cross-section of the elastic wave resonator 4 shown. The only structural difference between the elastic wave resonator 4B of this embodiment and the elastic wave resonator 4 of Embodiment 1 is that the thickness of the electrode fingers 14 is different between the first region 24A and the second region 24B, rather than the duty cycle of the electrode fingers 14 being different.

[0175] In this embodiment, such as Figure 19As shown, the first electrode finger group 14A located in the first region 24A has a first thickness D14A, and the second electrode finger group 14B located in the second region 24B has a second thickness D14B. In particular, in this embodiment, when the first pitch PA is less than the second pitch PB, the first thickness D14A is thicker than the second thickness D14B.

[0176] Figure 20 This is a graph showing the relationship between the thickness D14 of the electrode finger 14 of the elastic wave resonator 4B in this embodiment and the resonant frequency. Here, the thickness D14 of a certain electrode finger 14 is set to 100%, and the resonant frequency of the elastic wave oscillating in the main resonance mode is calculated by simulation when the thickness D14 of the electrode finger 14 is changed, and the result is plotted on [the graph]. Figure 20 In the diagram. Regarding Figure 20 The graph shows that the vertical axis represents frequency (in MHz), and the horizontal axis represents the percentage of the Al thickness of the material in electrode 14.

[0177] from Figure 20 As can be seen from this, the thinner the electrode finger 14 is, the higher the resonant frequency of the elastic wave oscillating in the main resonant mode tends to be.

[0178] In this embodiment, the first pitch PA is smaller than the second pitch PB, and the first thickness D14A is thicker than the second thickness D14B. Therefore, the difference between the first thickness D14A and the second thickness D14B acts in the direction of eliminating the difference in resonant frequency caused by the difference between the first pitch PA and the second pitch PB. In other words, in this embodiment, the resonant frequency effect characteristic that acts in the direction of eliminating the difference in resonant frequency caused by the size relationship between the pitches of the first electrode finger group 14A and the second electrode finger group 14B is the difference in thickness between the first electrode finger group 14A and the second electrode finger group 14B.

[0179] The frequency of the elastic wave excited in the stray mode has a different dependence on the thickness and spacing of the electrode fingers compared to the frequency of the elastic wave excited in the main resonance and anti-resonance modes. Therefore, in the elastic wave resonator 4B of this embodiment, similar to the elastic wave resonators 4 and 4A of the above embodiments, it is possible to reduce the intensity of stray waves while maintaining the uniformity of the resonant frequency.

[0180] Furthermore, in the elastic wave resonator 4B of this embodiment, the electrode finger arrangement region 24 includes a first region 24A and a second region 24B, but is not limited thereto. For example, similar to the previous embodiment, the electrode finger arrangement region 24 may also include an intermediate region 24C, which, when viewed from above, lies between the first region 24A and the second region 24B. In this case, the thickness of the intermediate electrode finger group 14C located in the intermediate region 24C can gradually change from the first region 24A side to the second region 24B side.

[0181] [Implementation Method Four]

[0182] <Differences in piezoelectric material thickness>

[0183] Figure 21 In the context of Figure 2 The diagram shows a schematic cross-sectional view of the elastic wave resonator 4C of this embodiment at the position corresponding to the cross-section of the elastic wave resonator 4 shown. The only structural difference between the elastic wave resonator 4C of this embodiment and the elastic wave resonator 4 of Embodiment 1 is that the thickness of the piezoelectric element 6 is different between the first region 24A and the second region 24B, rather than the duty cycle of the electrode fingers 14.

[0184] In this embodiment, such as Figure 21 As shown, the piezoelectric element 6 has different thicknesses between the first region 24A and the second region 24B. In particular, in this embodiment, the thickness of the piezoelectric element 6 gradually decreases from the end of the piezoelectric element 6 towards the center in the propagation direction TD.

[0185] piezoelectric element 6, for example Figure 21 As shown, the first region 24A has a first thickness D6A, and the second region 24B has a second thickness D6B. In particular, in this embodiment, when the first pitch PA is less than the second pitch PB, the first thickness D6A is thicker than the second thickness D6B.

[0186] Here, the thicknesses of the first thickness D6A and the second thickness D6B can vary depending on their positions in the first region 24A and the second region 24B, respectively. For example, the thicknesses of the first thickness D6A and the second thickness D6B gradually decrease from the end side to the center side of the piezoelectric body 6 in the propagation direction TD.

[0187] Furthermore, by adjusting the thickness of the sealing layer 28 according to the change in the thickness of the piezoelectric element 6, the overall thickness of the fixed substrate 36 can be kept approximately constant. In this embodiment, the thickness of the sealing layer 28 can, for example, gradually increase from the end of the sealing layer 28 towards the center in the propagation direction TD.

[0188] Figure 22This is a graph showing the relationship between the thickness of the piezoelectric element 6 of the elastic wave resonator 4C in this embodiment and the resonant frequency. Regarding... Figure 22 The graph shows the vertical axis representing frequency (MHz) and the horizontal axis representing the thickness of piezoelectric element 6 (μm). From Figure 22 As can be seen from this, the thinner the piezoelectric material 6 is, the higher the resonant frequency of the elastic wave oscillating in the main resonant mode tends to be.

[0189] In this embodiment, the first spacing PA is smaller than the second spacing PB, and the first thickness D6A is thicker than the second thickness D6B. Therefore, the difference between the first thickness D6A and the second thickness D6B acts in the direction of eliminating the difference in resonant frequency caused by the difference between the first spacing PA and the second spacing PB. In other words, in this embodiment, the resonant frequency effect characteristic that acts in the direction of eliminating the difference in resonant frequency caused by the size relationship between the spacing of the first electrode finger group 14A and the second electrode finger group 14B is the difference in the thickness of the piezoelectric body 6.

[0190] The frequency of the elastic wave excited in stray mode has a different dependence on the frequency of the elastic wave excited in main resonance and anti-resonance modes, depending on the spacing of the electrode fingers and the thickness of the piezoelectric element. Therefore, in the elastic wave resonator 4C of this embodiment, similar to the elastic wave resonators 4, 4A, and 4B of the above embodiments, it is possible to reduce the intensity of stray waves while maintaining the uniformity of the resonant frequency.

[0191] Furthermore, in the elastic wave resonator 4C of this embodiment, the electrode finger arrangement region 24 includes a first region 24A and a second region 24B, but is not limited thereto. For example, similar to Embodiment 2, the electrode finger arrangement region 24 may also include an intermediate region 24C between the first region 24A and the second region 24B when viewed from above.

[0192] Furthermore, in this embodiment, the thickness of the piezoelectric element 6 can gradually decrease from the end of the piezoelectric element 6 towards the center in the propagation direction TD, but is not limited to this. For example, the thickness of the piezoelectric element 6 can vary discontinuously at the boundary between the first region 24A and the second region 24B.

[0193] [Implementation Method Five]

[0194] <Differences in the thickness of reflective multilayer films>

[0195] Figure 23 In the context of Figure 2The diagram shows a schematic cross-sectional view of the elastic wave resonator 4D of this embodiment at the position corresponding to the cross-section of the elastic wave resonator 4 shown. The only structural difference between the elastic wave resonator 4D of this embodiment and the elastic wave resonator 4 of Embodiment 1 is that the thickness of the reflective multilayer film 30 is different between the first region 24A and the second region 24B, rather than the duty cycle of the electrode fingers 14.

[0196] In this embodiment, such as Figure 23 As shown, the reflective multilayer film 30 has different thicknesses between the first region 24A and the second region 24B. Specifically, in this embodiment, the thickness of the reflective multilayer film 30 gradually decreases from its ends towards the center in the propagation direction TD. In particular, in this embodiment, the thickness variation of the reflective multilayer film 30 is achieved by the respective thicknesses of the first layer 32 and the second layer 34 gradually decreasing from their ends towards the center.

[0197] For example, in the first layer 32 Figure 23 As shown, the first region 24A has a first thickness D32A, and the second region 24B has a second thickness D32B. Specifically, in this embodiment, when the first pitch PA is less than the second pitch PB, the first thickness D32A is thicker than the second thickness D32B. Similarly, the second layer 34, for example... Figure 23 As shown, the first region 24A has a first thickness D34A, and the second region 24B has a second thickness D34B. In particular, in this embodiment, when the first pitch PA is less than the second pitch PB, the first thickness D34A is thicker than the second thickness D34B.

[0198] Here, the first thickness D32A, the second thickness D32B, the first thickness D34A, and the second thickness D34B can have different thicknesses depending on their positions in the first region 24A and the second region 24B. For example, the thicknesses of the first thickness D32A, the second thickness D32B, the first thickness D34A, and the second thickness D34B gradually decrease from the end side to the center side of the reflective multilayer film 30 in the propagation direction TD.

[0199] Furthermore, by adjusting the thickness of the sealing layer 28 according to the change in the thickness of the reflective multilayer film 30, the overall thickness of the fixed substrate 36 can be kept approximately constant. In this embodiment, the thickness of the sealing layer 28 can, for example, gradually increase from the end of the sealing layer 28 towards the center in the propagation direction TD.

[0200] Figure 24 This is a graph showing the relationship between the thickness of the reflective multilayer film 30 of the elastic wave resonator 4D in this embodiment and the resonant frequency. Figure 24Figure 2401 is a graph calculated and plotted by simulation when the thickness D32 of a certain first layer 32 is set to 100% and the thickness D32 of the first layer 32 is changed. Figure 23 Figure 2402 is a graph calculated and plotted by simulation when the thickness D34 of a second layer 34 is set to 100% and the thickness D34 of the second layer 34 is changed.

[0201] about Figure 24 Figure 2401 shows the vertical axis representing frequency (in MHz) and the horizontal axis representing the percentage of the SiO2 thickness of the first layer 32. Regarding... Figure 24 Figure 2402 shows that the vertical axis represents frequency (unit: MHz), and the horizontal axis represents the percentage of the thickness of HfO2 in the second layer 34.

[0202] from Figure 24 As can be seen, the thinner the thickness D32 of the first layer 32 and the thickness D34 of the second layer 34, the higher the resonant frequency of the elastic wave oscillating in the main resonant mode tends to be. In other words, the thinner the reflective multilayer film 30, the higher the resonant frequency of the elastic wave oscillating in the main resonant mode tends to be.

[0203] In this embodiment, the first spacing PA is smaller than the second spacing PB, and the first thickness D32A and the second thickness D34A are thicker than the second thicknesses D32B and D34B, respectively. Therefore, the differences between the first thickness D32A and the second thickness D32B, and the differences between the first thickness D34A and the second thickness D34B, function in the direction of eliminating the difference in resonant frequency caused by the difference between the first spacing PA and the second spacing PB. In other words, in this embodiment, the resonant frequency function characteristic that functions in the direction of eliminating the difference in resonant frequency caused by the size relationship between the spacing of the first electrode finger group 14A and the second electrode finger group 14B is the difference in the thickness of the reflective multilayer film 30.

[0204] The frequency of the elastic wave excited in stray mode has a different dependence on the frequency of the elastic wave excited in main resonance and anti-resonance modes, depending on the spacing of the electrode fingers and the thickness of the reflective multilayer film. Therefore, in the elastic wave resonator 4D of this embodiment, similar to the elastic wave resonators 4, 4A to 4C of the above embodiments, it is possible to reduce the intensity of stray waves while maintaining the uniformity of the resonant frequency.

[0205] Furthermore, in the elastic wave resonator 4D of this embodiment, the electrode finger arrangement region 24 includes a first region 24A and a second region 24B, but is not limited thereto. For example, similar to Embodiment 2, the electrode finger arrangement region 24 may also include an intermediate region 24C between the first region 24A and the second region 24B when viewed from above.

[0206] Furthermore, in this embodiment, the thickness of the reflective multilayer film 30 can gradually change from the end of the reflective multilayer film 30 towards the center in the propagation direction TD, but is not limited to this. For example, the thickness of the reflective multilayer film 30 can change discontinuously at the boundary between the first region 24A and the second region 24B.

[0207] [Implementation Method Six]

[0208] <Protective film>

[0209] Figure 25 In the context of Figure 2 This is a schematic cross-sectional view of the elastic wave resonator 4E of this embodiment at the location corresponding to the cross-section of the elastic wave resonator 4 shown. Compared to the elastic wave resonator 4 of Embodiment 1, the elastic wave resonator 4E of this embodiment has the following characteristics: Figure 25 As shown, a protective film 38 is provided at the position covering the uppermost surface of the elastic wave resonator 4E. In other words, the elastic wave resonator 4E of this embodiment is provided with a protective film 38 at the positions covering the upper surface of the piezoelectric body 6, the upper surface and side of the IDT electrode 8 and the reflector 18, respectively.

[0210] The protective film 38 is a thin film used to protect the electrodes on the piezoelectric body 6 from corrosion of the IDT electrode 8 and reflector 18. For example, SiO2 or Si3N4 can be used for the protective film 38. Furthermore, the protective film 38 can be provided by stacking multiple layers formed of the above-mentioned materials. These materials are suitable for the protective film 38 due to their high insulation and low weight. However, the materials for the protective film 38 are not limited to these.

[0211] In this embodiment, such as Figure 25 As shown, the protective film 38 has different thicknesses between the first region 24A and the second region 24B. Conversely, in this embodiment, the duty cycle of the electrode fingers 14 of the IDT electrode 8 is constant. In this embodiment, the protective film 38 may gradually decrease in thickness from its end to its center in the propagation direction TD, or it may vary discontinuously at the boundary between the first region 24A and the second region 24B.

[0212] Protective film 38, for example Figure 26As shown, the first region 24A has a first thickness D38A, and the second region 24B has a second thickness D38B. In particular, in this embodiment, when the first pitch PA is less than the second pitch PB, the first thickness D38A is thicker than the second thickness D38B.

[0213] Apart from the points mentioned above, the structure of the elastic wave resonator 4E in this embodiment can be the same as the structure of the elastic wave resonator 4 in Embodiment 1.

[0214] Figure 26 This is a graph showing the relationship between the thickness of the protective film 38 of the elastic wave resonator 4E in this embodiment and the resonant frequency. Here, the thickness of a certain protective film 38 is set to 100%, and the resonant frequency of the elastic wave oscillating in the main resonance mode is calculated by simulation when the thickness of the protective film 38 is changed, and the result is plotted on [the graph]. Figure 26 In the diagram. Regarding Figure 26 The graph shows that the vertical axis represents frequency (unit: MHz), and the horizontal axis represents the percentage of the thickness of the protective film 38.

[0215] from Figure 26 As can be seen from this, the thinner the protective film 38, the higher the resonant frequency of the elastic wave oscillating in the main resonance mode tends to be.

[0216] In this embodiment, the first spacing PA is smaller than the second spacing PB, and the first thickness D38A is thicker than the second thickness D38B. Therefore, the difference between the first thickness D38A and the second thickness D38B acts in the direction of eliminating the difference in resonant frequency caused by the difference between the first spacing PA and the second spacing PB. In other words, in this embodiment, the resonant frequency effect characteristic that acts in the direction of eliminating the difference in resonant frequency caused by the size relationship between the spacing of the first electrode finger group 14A and the second electrode finger group 14B is the difference in the thickness of the protective film 38.

[0217] The frequency of the elastic wave excited in stray mode has a different dependence on the frequency of the elastic wave excited in main resonance and anti-resonance modes, depending on the spacing of the electrode fingers and the thickness of the piezoelectric element. Therefore, in the elastic wave resonator 4E of this embodiment, similar to the elastic wave resonators 4, 4A to 4D of the above embodiments, it is possible to reduce the intensity of stray waves while maintaining the uniformity of the resonant frequency.

[0218] Furthermore, in the elastic wave resonator 4E of this embodiment, the electrode finger arrangement region 24 includes a first region 24A and a second region 24B, but is not limited thereto. For example, similar to Embodiment 2, the electrode finger arrangement region 24 may also include an intermediate region 24C between the first region 24A and the second region 24B when viewed from above. In this case, the thickness of the protective film 38 preferably gradually changes from the end of the protective film 38 towards the center in the propagation direction TD.

[0219] Furthermore, the elastic wave resonators 4, 4A to 4D in the above embodiments may also have a thin film formed at the position covering the uppermost surface of the elastic wave resonator 4E, similar to the protective film 38 in this embodiment. However, when the elastic wave resonators 4, 4A to 4D in the above embodiments have this thin film, the film may have a thickness distribution within the surface, or it may be formed approximately uniformly.

[0220] [Implementation Method Seven]

[0221] <Spacing of the bar electrodes of the reflector>

[0222] Figure 27 This is a schematic top view showing an enlarged view of the periphery of the reflector 18 of the elastic wave resonator 4G in this embodiment. The elastic wave resonator 4G of this embodiment, for example, may have the same structure as the elastic wave resonators of the above-described embodiments, except for the structure of the reflector 18. Furthermore, Figure 27 The reflector 18 shown is Figure 1 Compared to the reflector 18 shown above, the number of strip electrodes 22 is different. However, the elastic wave resonator of each of the above embodiments may also include: having the same... Figure 27 The reflector 18 shown has the same number of strip electrodes 22 as the reflector 18.

[0223] like Figure 27 As shown, the elastic wave resonator 4G of this embodiment includes an electrode finger configuration region 24 in the region including the strip electrode 22 of the reflector 18. In this embodiment, the electrode finger configuration region 24 includes at least a first region 24A and a second region 24B. Furthermore, the strip electrode 22 includes: a first strip electrode group 22F, which is a first electrode finger group located in the first region 24F; and a second strip electrode group 22G, which is a second electrode finger group located in the second region 24B.

[0224] Furthermore, in this embodiment, when the elastic wave resonator 4G includes a pair of reflectors 18, electrode finger configuration regions 24 may also be formed in each reflector 18. Additionally, the electrode finger configuration regions 24 may include at least one of a first region 24F and a second region 24G. For example, as... Figure 27 As shown, in the propagation direction TD, the electrode finger configuration region 24 symmetrically includes the first region 24F with respect to the second region 24G.

[0225] Here, each of the plurality of strip electrodes 22 is arranged at a certain spacing from each other, similar to the electrode fingers 14. Furthermore, the first spacing PF of the first strip electrode group 22F differs from the second spacing PG of the second strip electrode group 22G.

[0226] Furthermore, the duty cycle of the first strip electrode group 22F differs from that of the second strip electrode group 22G. Specifically, the duty cycles of the first strip electrode group 22F and the second strip electrode group 22G are designed to eliminate the effect of the difference in resonant frequency caused by the difference between the first spacing PF and the second spacing PG. In particular, when the first spacing PF is smaller than the second spacing PG, the duty cycle of the first strip electrode group 22F is greater than that of the second strip electrode group 22G.

[0227] Here, the frequency of the elastic wave excited in stray mode has a different dependence on the frequency of the elastic wave excited in main resonance and anti-resonance modes, relative to the changes in the duty cycle and spacing of the strip electrodes of the reflector. Therefore, the elastic wave resonator 4G includes: a first strip electrode group 22F and a second strip electrode group 22G with different spacing and duty cycles and smaller differences in resonant frequencies.

[0228] Therefore, between the first region 24F and the second region 24G, the frequency uniformity of the elastic wave excited in the main resonant mode can be further maintained, and the frequencies of the elastic waves excited in the spurious mode can be made more distinct. Thus, according to this embodiment, within the same elastic wave resonator 4G, by maintaining the uniformity of the resonant frequency and dispersing the frequencies of the elastic waves excited in the spurious mode, the intensity of spurious waves can be reduced.

[0229] Furthermore, in this embodiment, the thicknesses of the strip electrode 22, piezoelectric element 6, reflective multilayer film 30, or protective film 38 can also be different between the first region 24F and the second region 24G, instead of the duty cycle of the strip electrode 22. In this case, these thickness differences are designed to eliminate the effect of the difference in resonant frequency caused by the difference between the first spacing PF and the second spacing PG.

[0230] <Other variations>

[0231] In each of the above embodiments, examples were given of individually changing the duty cycle of the electrode fingers, the thickness of the electrode fingers, the thickness of the piezoelectric element 6, the thickness of the reflective multilayer film 30, and the thickness of the protective film 38, with respect to the spacing of the electrode fingers. However, this disclosure is not limited to this, and the structures of the elastic wave resonators 4, 4A to 4G can also be combined separately.

[0232] For example, in a region where the spacing between the electrode fingers is larger than in one region, the duty cycle of the electrode fingers in that region can be narrowed, and the thickness of the protective film 38 can be reduced. Thus, compared to adjusting the resonant frequency using only one element, the adjustment amount of each element can be reduced, while achieving the same effect.

[0233] Furthermore, in each embodiment, examples have been described in which at least one of the regions including the IDT electrode 8 and the region including the reflector 18 in the elastic wave resonators 4, 4A to 4G includes both a first region and a second region. However, the embodiments are not limited to this; the first region may be formed only in the region including the IDT electrode 8, and the second region may be formed only in the region including the reflector 18.

[0234] In other words, in various embodiments, all electrode fingers 14 of the IDT electrode 8 can be included in the first electrode finger group, and all strip electrodes 22 of the reflector 18 can be included in the second electrode finger group. In this case, the spacing between the electrode fingers 14 and the strip electrodes 22 is different, and it is designed to eliminate the difference in resonant frequency caused by the difference in the spacing between the electrode fingers 14 and the strip electrodes 22. Alternatively, in the above case, the spacing within the electrode fingers 14 or the strip electrodes 22 can also be constant.

[0235] Furthermore, in each embodiment, examples of elastic wave resonators 4, 4A to 4G including a reflective multilayer film 30 have been described. However, this disclosure is not limited to this; the fixed substrate 36 of the elastic wave resonators 4, 4A to 4G may also have the piezoelectric element 6 directly formed on the Si support substrate 26, or may include an insulating layer formed of SiO2 or the like instead of the reflective multilayer film 30.

[0236] Furthermore, in the elastic wave resonators 4, 4A to 4G of each embodiment, a gap may exist between the inner side of the region where the IDT electrode 8 is formed in the piezoelectric body 6 and the support substrate 26. In this case, the elastic wave resonators 4, 4A to 4G of each embodiment may also be, for example, a so-called film-like structure in which the piezoelectric body 6 is disposed on the support substrate 26 having a recess.

[0237] Other embodiments of the elastic wave resonator disclosed herein include: a piezoelectric element; and an IDT electrode having a plurality of electrode fingers located on the piezoelectric element and arranged in the direction of propagation of the elastic wave; the region where the plurality of electrode fingers are located includes a first region and a second region when viewed from above; the plurality of electrode fingers include: a first group of electrode fingers located in the first region and a second group of electrode fingers located in the second region; the spacing of the first group of electrode fingers is different from the spacing of the second group of electrode fingers; the first region and the second region have frequency-dependent characteristics that act in a direction that eliminates the effect of the magnitude relationship of the resonant frequency caused by the magnitude relationship of the spacing of each group of electrode fingers.

[0238] In other embodiments of the elastic wave resonator disclosed herein, the above embodiments further include: a support substrate located on the side opposite to the IDT electrode, which is further away from the piezoelectric element; and a reflective multilayer film between the piezoelectric element and the support substrate; the frequency response characteristic is the difference in thickness between the reflective multilayer film in the first region and the second region.

[0239] In other embodiments of the elastic wave resonator disclosed herein, in any of the above embodiments, a pair of reflectors are further included on the piezoelectric element at opposite ends of the plurality of electrodes in the propagation direction.

[0240] Other embodiments of the elastic wave resonator disclosed herein include: a piezoelectric element; and an IDT electrode having a plurality of electrode fingers located on the piezoelectric element and arranged in the direction of propagation of the elastic wave; the region where the plurality of electrode fingers are located includes a first region and a second region when viewed from above; among the plurality of electrode fingers, the spacing of a first electrode finger group located in the first region is smaller than that of a second electrode finger group located in the second region, and the duty cycle of the first electrode finger group is larger than that of the second electrode finger group.

[0241] <An overview of the structure of communication devices and demultiplexers>

[0242] Figure 28 This is a block diagram of the main parts of the communication device 40 according to an embodiment of the present invention. The communication device 40 uses radio waves for wireless communication. The demultiplexer 42 has the function of demultiplexing the signal at the transmission frequency and the signal at the reception frequency in the communication device 40.

[0243] In the communication device 40, the transmission information signal TIS, which includes the information to be transmitted, is modulated and frequency-boosted (converted into a high-frequency signal at the carrier frequency) by the RF-IC 44, thus becoming the transmission signal TS. The transmission signal TS is passed through a bandpass filter 46 to remove unnecessary components outside the transmission passband, and then amplified by an amplifier 48 before being input to a demultiplexer 42. The demultiplexer 42 removes unnecessary components outside the transmission passband from the input transmission signal TS and outputs it to the antenna 50. The antenna 50 converts the input electrical signal (transmission signal TS) into a wireless signal and transmits it.

[0244] In the communication device 40, the wireless signal received through the antenna 50 is converted into an electrical signal (received signal RS) and input to the demultiplexer 42. The demultiplexer 42 removes unnecessary components outside the passband from the input received signal RS and outputs it to the amplifier 52. The output received signal RS is amplified by the amplifier 52 and then passes through the bandpass filter 54 to remove unnecessary components outside the passband. The received signal RS is then frequency-reduced and demodulated by the RF-IC 44 to become the received information signal RIS.

[0245] Furthermore, the Transmit Information Signal (TIS) and the Receive Information Signal (RIS) can be low-frequency signals (baseband signals) containing appropriate information, such as analog or digitized audio signals. The wireless signal passband can conform to various standards such as UMTS (Universal Mobile Telecommunications System). Modulation methods can be phase modulation, amplitude modulation, frequency modulation, or any combination of two or more of these.

[0246] Figure 29 This is a circuit diagram illustrating the structure of a demultiplexer 42 according to one embodiment of the present invention. The demultiplexer 42 is... Figure 28 The demultiplexer 42 used in the communication device 40.

[0247] like Figure 29As shown, the transmitting filter 56 includes series resonators S1-S3 and parallel resonators P1-P3. The demultiplexer 42 mainly consists of an antenna terminal 58, a transmitting terminal 60, a receiving terminal 62, a transmitting filter 56 disposed between the antenna terminal 58 and the transmitting terminal 60, and a receiving filter 64 disposed between the antenna terminal 58 and the receiving terminal 62. The transmitting signal TS from the amplifier 48 is input to the transmitting terminal 60. The transmitting signal TS input to the transmitting terminal 60 is filtered in the transmitting filter 56 to remove unnecessary components outside the passband used for transmission, and then output to the antenna terminal 58. Additionally, the receiving signal RS from the antenna 50 is input to the antenna terminal 58. The receiving filter 64 removes unnecessary components outside the passband used for reception, and then output to the receiving terminal 62.

[0248] The transmitting filter 56 is, for example, a trapezoidal elastic wave filter. Specifically, the transmitting filter 56 has: three series resonators S1, S2, and S3 connected in series between its input and output sides; and three parallel resonators P1, P2, and P3 disposed between the series arm and the reference potential section G; the series arm is wiring for connecting the series resonators. That is, the transmitting filter 56 is a trapezoidal filter with a three-stage structure. However, in the transmitting filter 56, the number of stages of the trapezoidal filter is arbitrary.

[0249] An inductor L is provided between the parallel resonators P1 to P3 and the reference potential section G. By setting the inductance of the inductor L to a predetermined value, an attenuation pole is formed outside the passband of the transmitted signal, thereby increasing the attenuation outside the frequency band. The multiple series resonators S1 to S3 and the multiple parallel resonators P1 to P3 are each composed of elastic wave resonators.

[0250] The receiving filter 64 includes, for example, a multi-mode elastic wave filter 66 and an auxiliary resonator 68 connected in series with its input side. Furthermore, in this embodiment, multi-mode includes dual-mode. The multi-mode elastic wave filter 66 has a balun function, and the receiving filter 64 is connected to the two receiving terminals 62 that output a balanced signal. The receiving filter 64 is not limited to being composed of a multi-mode elastic wave filter 66; it can also be composed of a trapezoidal filter, or it can be a filter without a balun function.

[0251] An impedance matching circuit, consisting of an inductor or the like, can be inserted between the connection point of the transmitting filter 56, the receiving filter 64, and the antenna terminal 58 and the ground potential section G.

[0252] The elastic wave filters in the above embodiments are, for example, made of... Figure 28The elastic wave element is composed of a ladder-shaped filter circuit of at least one of the transmitting filter 56 or the receiving filter 64 in the shown splitter 42. When either the transmitting filter 56 or the receiving filter 64 is an elastic wave filter of the above embodiments, all or at least a portion of the elastic wave resonators included in the filter are elastic wave resonators 4, 4A to 4G of the above embodiments.

[0253] By employing a demultiplexer 42 that includes such a transmit filter 56 or a receive filter 64, the filter characteristics of the communication device 40 can be improved.

[0254] This invention is not limited to the embodiments described above, and various modifications can be made within the scope of the claims; embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of this invention.

[0255] Explanation of reference numerals in the attached figures

[0256] 2… Elastic wave filter, 4, 4A~4G… Elastic wave resonator, 6… Piezoelectric element, 8… IDT electrode, 12, 20… Busbar, 14… Electrode finger, 14A… First electrode finger group, 14B… Second electrode finger group, 14C… Intermediate electrode finger group, 14D… First intermediate electrode finger group, 14E… Second intermediate electrode finger group, 18… Reflector, 22… Strip electrode, 24… Electrode finger configuration area, 24A… First area, 24B… Second area, 24C… Intermediate area, 24D… First intermediate area, 24D… Second intermediate area, 26… Support substrate, 30… Reflective multilayer film, 38… Protective film, 40… Communication device, 42… Demultiplexer, 44… RF-IC, 50… Antenna, 56… Transmit filter, 58… Antenna terminal, 64… Receive filter.

Claims

1. An elastic wave resonator, including: piezoelectric elements; and, Multiple electrodes located on the piezoelectric body and arranged in the direction of elastic wave propagation; The multiple electrodes refer to the area where they are located, which, when viewed from above, includes a first area and a second area; The plurality of electrode fingers includes: a first electrode finger group located in the first region and a second electrode finger group located in the second region; The spacing between the first electrode finger group and the spacing between the second electrode finger group are different; The first region and the second region have frequency-dependent characteristics that act in the direction of eliminating the effect of the high or low resonant frequency or anti-resonant frequency caused by the size relationship of the spacing of each electrode finger group. The elastic wave resonator described above comprises: A protective film formed of insulating material is located on the plurality of electrode fingers; The frequency-dependent characteristics include the difference in thickness between the protective film in the first region and the second region.

2. The elastic wave resonator according to claim 1, wherein the frequency response characteristic includes the difference in duty cycle between the electrode fingers in the first region and the second region.

3. The elastic wave resonator according to claim 1, wherein the frequency response characteristics include the difference in thickness between the electrode fingers in the first region and the second region.

4. The elastic wave resonator according to claim 1, wherein the frequency response characteristics include the difference in thickness of the piezoelectric element in the first region and the second region.

5. The elastic wave resonator according to claim 1, further comprising: The supporting substrate is located on the side opposite to the electrode finger, which is closer to the piezoelectric element; and, The reflective multilayer film between the piezoelectric element and the supporting substrate; The frequency-dependent characteristics include the difference in thickness between the reflective multilayer films in the first region and the second region.

6. The elastic wave resonator according to claim 1, wherein the resonant frequency of the main resonance of the elastic wave in the first region is the same as the resonant frequency of the main resonance of the elastic wave in the second region.

7. The elastic wave resonator according to any one of claims 1 to 6, wherein the region where the plurality of electrodes are located, when viewed from above, also includes an intermediate region different from the first region and the second region; The plurality of electrode fingers also includes an intermediate electrode finger group located in the intermediate region; The spacing between the intermediate electrode finger groups is the value between the spacing between the first electrode finger groups and the spacing between the second electrode finger groups; The resonant frequency of the main resonance of the elastic wave in the intermediate region is a value between the resonant frequency of the main resonance of the elastic wave in the first region and the resonant frequency of the main resonance of the elastic wave in the second region.

8. The elastic wave resonator according to claim 7, wherein, when viewed from above, the intermediate region is included between the first region and the second region; The spacing of the intermediate electrode fingers gradually changes from the first region to the second region.

9. The elastic wave resonator according to claim 8, wherein the intermediate region comprises: The spacing of the intermediate electrode finger group gradually changes from the first region to the second region according to a first variation amount in the first intermediate region; And, the spacing of the intermediate electrode finger group gradually changes from the first region to the second region according to a second change amount different from the first change amount in the second intermediate region.

10. The elastic wave resonator according to claim 8, wherein the amount of variation in the spacing of the intermediate electrode finger group gradually changes from the first region to the second region.

11. The elastic wave resonator according to any one of claims 1 to 6, comprising: At least one of the multiple first regions and the second region; In the propagation direction, symmetrically included relative to one of the first region and the second region is the other of the first region and the second region.

12. The elastic wave resonator according to any one of claims 1 to 6, wherein the piezoelectric body includes an IDT electrode, the IDT electrode including at least a portion of the plurality of electrode fingers.

13. The elastic wave resonator according to any one of claims 1 to 6, wherein the piezoelectric element comprises: IDT electrode, wherein the IDT electrode includes a portion of the plurality of electrode fingers; and, a pair of reflectors, the pair of reflectors being located at opposite ends of the propagation direction relative to the IDT electrodes, each comprising the other portions of the plurality of electrodes.

14. The elastic wave resonator according to any one of claims 1 to 6, wherein the resonant frequency in more than 80% of the region where the plurality of electrodes are located is the same as the resonant frequency of the elastic wave in the first region.

15. The elastic wave resonator according to any one of claims 1 to 6, wherein the thickness of the piezoelectric element is less than or equal to the spacing in the first electrode finger group or the second electrode finger group.

16. The elastic wave resonator according to any one of claims 1 to 6, wherein among the plurality of electrode fingers, the spacing of the first electrode finger group located in the first region is smaller than that of the second electrode finger group located in the second region, and the duty cycle of the first electrode finger group is larger than that of the second electrode finger group.

17. An elastic wave filter, comprising at least one elastic wave resonator according to any one of claims 1 to 6.

18. A demultiplexer, including: Antenna terminals; A transmission filter is used to filter the transmitted signal and output it to the antenna terminal; and, A receiving filter is used to filter the received signal from the antenna terminal. At least one of the transmitting filter and the receiving filter includes the elastic wave filter of claim 17.

19. A communication device, comprising: antenna; The demultiplexer of claim 18, wherein the antenna terminal is connected to the antenna; and, An IC connected to the transmitting filter and the receiving filter.

Images