Elastic wave device

Abstract

The invention discloses an elastic wave device, and the elastic wave device comprises a piezoelectric layer; an IDT electrode formed on the piezoelectric layer; the IDT electrode comprises a first bus bar and a second bus bar which are opposite to each other; in a plan view, the first bus bar and the second bus bar are provided with a plurality of step portions parallel to the propagation direction of surface acoustic waves on the sides of the first bus bar and the second bus bar facing each other, and the step portions adjacent to each other are provided at different positions in the direction from the first bus bar to the second bus bar. A step part is arranged between every two adjacent step parts; in a top view, the distance between the step portion of the first bus bar and the step portion of the second bus bar is the same as the distance between the opposite step portions of the first bus bar and the second bus bar.

Description

Technical Field

[0001] This invention relates to the field of mobile communication equipment, and more specifically to an elastic wave device. Background Technology

[0002] As a surface acoustic wave (SAW) device utilizing surface acoustic waves, a surface acoustic wave (SAW) resonator with an IDT (Interdigital Transducer) electrode disposed on the main surface of a piezoelectric substrate is known. This SAW resonator can be used, for example, as a transmit filter and receive filter in a demultiplexer. In this type of surface acoustic wave device, a transverse mode is generated. This transverse mode introduces adverse effects such as spurious emissions and losses in the passband and therefore should be suppressed.

[0003] Patent document 1 (Japanese Patent Application Publication No. 2020-92422) discloses an IDT electrode having curved segments formed in a specific arrangement, which causes the waveguide of the elastic wave device to generate curvature, thereby suppressing the transverse mode of the elastic wave device.

[0004] Patent document 2 (Japanese Patent Application Publication No. 2000-286663) discloses an elastic wave device (SAW resonator) that, in order to suppress the transverse mode of the elastic wave device, makes the transverse mode reflected by the busbar on one side cancel each other out with the transverse mode reflected by the busbar on the other side, thereby effectively suppressing the transverse mode. Summary of the Invention

[0005] The present invention aims to provide a device capable of suppressing transverse mode elastic waves.

[0006] An elastic wave device, comprising: piezoelectric layer; IDT electrodes formed on the piezoelectric layer; The IDT electrode includes a first busbar and a second busbar that are opposite to each other; In the top view, the first busbar and the second busbar are provided with a plurality of stepped portions parallel to the direction of propagation of the elastic surface wave on the side of the first busbar and the second busbar facing each other, and the stepped portions adjacent to each other are located at different positions along the direction from the first busbar to the second busbar. A step is provided between adjacent stepped sections; In the top view, the stepped portion of the first busbar and the stepped portion of the second busbar are equidistant from each other.

[0007] In some embodiments of the present invention, the elastic wave device is an elastic surface wave device, and when the wavelength of the elastic surface wave is λ, the width of the step portion perpendicular to the propagation direction of the elastic surface wave is less than 1.5λ.

[0008] In some embodiments of the present invention, the first busbar and the second busbar include three stepped portions, namely a first stepped portion, a second stepped portion adjacent to the first stepped portion, and a third stepped portion adjacent to the second stepped portion; A step is provided between the first step and the second step, and the step is formed along the direction from the first busbar toward the second busbar. A step is provided between the second step and the third step, and the step is formed along the direction from the second step to the third step, in the direction from the second busbar to the first busbar.

[0009] In some embodiments of the present invention, the first busbar and the second busbar respectively include: a first step portion, a second step portion adjacent to the first step portion, a step portion disposed between the first step portion and the second step portion, a third step portion adjacent to the second step portion, and a step portion disposed between the second step portion and the third step portion; As the first step, the second step, and the third step change in sequence, steps are formed in the same direction, and the direction of the step is: from the second busbar toward the first busbar, or from the first busbar toward the second busbar.

[0010] In some embodiments of the present invention, in a top view, the first busbar and the second busbar are provided with a plurality of stepped portions parallel to the direction of propagation of the elastic surface wave on opposite sides, and a step portion is provided between adjacent stepped portions. When the wavelength of the elastic wave is λ, the total height of the step portion in the direction from the first busbar to the second busbar is less than 2.0λ.

[0011] In some embodiments of the present invention, in a top view, the first busbar and the second busbar are provided with a plurality of stepped portions parallel to the direction of propagation of the elastic surface wave on opposite sides, and a step portion is provided between adjacent stepped portions, the step portion being formed in a direction perpendicular to the direction of propagation of the elastic surface wave.

[0012] In some embodiments of the present invention, in a top view, the first busbar and the second busbar are provided with a plurality of stepped portions parallel to the propagation direction of the elastic surface wave on opposite sides, and a step portion is provided between adjacent stepped portions. One side has a plurality of ends arranged along an inclined virtual line, the virtual line being inclined to the propagation direction of the elastic wave.

[0013] In some embodiments of the present invention, in a top view of the IDT electrode, the first busbar and the second busbar respectively include a first flat region, a second flat region, a third flat region, and a sloping region disposed between adjacent flat regions.

[0014] In some embodiments of the present invention, the IDT electrode further includes a plurality of electrode fingers extending from the first bus bar to the second bus bar, a plurality of electrode fingers extending from the second bus bar to the first bus bar, and dummy electrodes respectively facing the electrode fingers, wherein a gap is formed between the end of the electrode fingers and the dummy electrodes, and the slope region is the region where the base of the electrode fingers or the base of the dummy electrodes are arranged along an inclined virtual line.

[0015] In some embodiments of the present invention, the slope region is a step between adjacent stepped portions, wherein the step portion is provided with at least one base of the electrode finger or a base of the dummy electrode, such that the bases of adjacent electrode fingers or the bases of adjacent dummy electrodes are arranged at an angle to form a slope structure and thus form the slope region.

[0016] According to the present invention, since adjacent stepped portions are provided on the first and second busbars of the IDT electrode, and these stepped portions are provided at different positions in the direction from the first busbar to the second busbar, it is possible to realize an elastic wave device that suppresses transverse modes.

[0017] Other features and advantages of the invention will be set forth in the following description, and will be apparent in part from the description, or may be learned by practicing the invention. Attached Figure Description

[0018] The accompanying drawings, which are provided to further illustrate this application and form part of this application, illustrate exemplary embodiments of this application and are used to explain this application, but do not constitute an undue limitation of this application.

[0019] Figure 1 A cross-sectional view illustrating one embodiment of the elastic wave device of the present invention.

[0020] Figure 2 This is a plan view showing the IDT electrode of the elastic wave device according to the first embodiment of the present invention.

[0021] Figure 3a A graph illustrating the relationship between the real admittance and frequency of the elastic wave device of Example 1.

[0022] Figure 3b A graph showing the relationship between the real admittance and frequency of the elastic wave device of Example 2.

[0023] Figure 3c A graph showing the relationship between the real admittance and frequency of a comparative elastic wave device.

[0024] Figure 4 A graph showing the relationship between the real admittance and frequency of the elastic wave devices of Examples 1, 2 and the comparative example is provided.

[0025] Figure 5 This is a plan view of the IDT electrodes of a comparative elastic wave device.

[0026] Figure 6 A graph showing the relationship between the real admittance and frequency of the elastic wave device in both Example 3 and the comparative example is provided.

[0027] Figure 7 This is a plan view of the IDT electrode of the elastic wave device according to the second embodiment of the present invention.

[0028] Figure 8a A graph showing the change in the real part of the admittance versus frequency of the elastic wave device in Example 4 is provided.

[0029] Figure 8b A graph showing the change in the real part of the admittance versus frequency of the elastic wave device of Example 5 is provided.

[0030] Figure 8c A graph showing the variation of the real part of the admittance with frequency for a comparative elastic wave device.

[0031] Figure 9 The graphs showing the changes in the real part of the admittance and frequency of the elastic wave devices in Examples 4, 5 and the comparative examples are presented simultaneously.

[0032] Figure 10 This is a plan view of the IDT electrode of the elastic wave device according to the third embodiment of the present invention.

[0033] Figure 11 This is a plan view showing the IDT electrode of the elastic wave device according to the fourth embodiment of the present invention.

[0034] Figure 12 This is a plan view of the IDT electrode of the elastic wave device according to the fifth embodiment of the present invention.

[0035] Figure 13 This is a partially enlarged view of the IDT electrode according to the fifth embodiment of the present invention.

[0036] Figure 14 This is a plan view of the IDT electrode of the elastic wave device according to the sixth embodiment of the present invention.

[0037] Explanation of symbols: 1 - Elastic wave devices 2 - Support substrate 3 - Piezoelectric layer 4 - IDT Electrode 5 - Reflectors 6 - Intermediate Layer 11a - First busbar 11b - Second busbar 12a - Electrode finger 12b - Electrode finger 21a, 21b, 22a, 22b, 23a, 23b - Stepped section 31a, 31b, 32a, 32b - Stepped sections 91, 92, 93, 95, 96 - Slope area. Detailed Implementation

[0038] The following will refer to Figures 1 to 9 Typical embodiments of the present invention are described below. The elastic wave device 1 according to this embodiment is suitable for use as a frequency filter in mobile communication devices, etc. In the figures, the same or corresponding parts are labeled with the same symbols. Repeated descriptions of corresponding parts are appropriately simplified or omitted.

[0039] <First Implementation> Figure 1 This is a cross-sectional view showing a first embodiment of the elastic wave device. The elastic wave device 1 is a SAW resonator, including: a support substrate 2, a piezoelectric layer 3, an IDT electrode 4 formed on the piezoelectric layer 3, and an intermediate layer 6 disposed between the support substrate 2 and the piezoelectric layer 3.

[0040] Figure 2 This is a plan view showing the IDT electrode 4 and reflector 5 disposed on the main surface of the piezoelectric layer 3 in the elastic wave device 1. Figure 2 In the IDT electrode 4, the IDT electrode 4 includes: a first bus bar 11a, a second bus bar 11b, a plurality of electrode fingers 12a extending from the first bus bar 11a to the second bus bar 11b, a plurality of electrode fingers 12b extending from the second bus bar 11b to the first bus bar 11a, and dummy electrodes 15a and 15b respectively facing the electrode fingers 12a and 12b. Gap gaps 17b and 17a are formed between the ends 13a and 13b of the electrode fingers 12a and 12b and the dummy electrodes 15b and 15a, respectively.

[0041] Busbar 11a and busbar 11b are connected to the input terminal (not shown) and the output terminal (not shown), respectively. When a high-frequency signal is input to the input terminal and the output terminal, an electric field is generated between the electrodes, thereby exciting a surface elastic wave. This surface elastic wave propagates on the piezoelectric layer 3 and is reflected at the reflector 5, thus generating an electrical resonance. The resonance frequency fR is determined by the following relationship: when the wavelength of the surface elastic wave propagating on the piezoelectric layer 3 is λ and the electrode period is P, the condition P = λ / 2 is satisfied.

[0042] The material used for the support substrate 2 can be, for example, crystalline silicon or crystalline sapphire. The material of the support substrate 2 is not limited to the above-mentioned materials; other materials such as polycrystalline silicon, polycrystalline alumina, and spinel can also be used, as long as they can solve the technical problem of this invention.

[0043] Lithium tantalate (LiTaO3) or lithium niobate (LiNbO3) can be used as the material for the piezoelectric layer 3. However, the material for the piezoelectric layer 3 is not limited to the above materials, and other materials can also be used.

[0044] The purpose of the intermediate layer 6 is at least to improve the bonding strength between the support substrate 2 and the piezoelectric layer 3, or to accelerate the propagation speed of elastic waves.

[0045] The IDT electrode 4 can be made of materials such as Al, Au, Cu, Ni, Pt, Ti, Cr, Ag, or alloys thereof, but other metals or alloys may also be used. Furthermore, the IDT electrode 4 can also be constructed by stacking the aforementioned metals or alloys.

[0046] When the purpose of setting the intermediate layer 6 is to improve the bonding strength between the support substrate 2 and the piezoelectric layer 3, materials such as silicon dioxide (SiO2) can be used.

[0047] When the function of intermediate layer 6 is to accelerate the propagation speed of elastic waves, aluminum nitride (AlN) or boron aluminum nitride (B) can be used. X Al 1-X Materials such as N). Furthermore, in this embodiment, the intermediate layer 6 may be omitted.

[0048] When manufacturing the elastic wave device 1, the piezoelectric layer 3 can be, for example, lithium tantalate (LiTaO3) with a 36°Y cut X-propagation or a 42°Y cut X-propagation.

[0049] like Figure 2 As shown, in a top view (plan view), the first and second busbars in the IDT electrode 4 have multiple sections along the elastic surface wave propagation direction on the side where the first busbar 11a and the second busbar 11b face each other. Figure 2The first busbar 11a has a stepped portion parallel to the X direction. The first busbar 11a has a first stepped portion 21a, a second stepped portion 22a, and a third stepped portion 23a. The second busbar 11b has a first stepped portion 21b, a second stepped portion 22b, and a third stepped portion 23b. These stepped portions, along with the stepped portions described later, create a stepped structure on the opposite sides of the busbars 11a and 11b.

[0050] IDT electrode 4 in Figure 2 The X-direction indicated by the arrow shows three parts: the first flat region 51, the second flat region 52, and the third flat region 53. The first flat region 51, the second flat region 52, and the third flat region 53 correspond to the regions where the first step 21a, the second step 22a, and the third step 23a are located, respectively.

[0051] The first step portion 21a is located at the height of the virtual line L1a. (In this embodiment, "height" refers to the extension direction of the electrode fingers, that is, the height in the direction parallel to the direction from the first busbar to the second busbar.) The second step portion 22a is located at the height of the virtual line L2a, and the third step portion 23a is located at the height of the virtual line L3a. Similarly, the first step portion 21b is located at the height of the virtual line L1b, the second step portion 22b is located at the height of the virtual line L2b, and the third step portion 23b is located at the height of the virtual line L3b. Furthermore, the spacing between opposing step portions is equal. That is, the distance between virtual lines L1a and L1b, the distance between virtual lines L2a and L2b, and the distance between virtual lines L3a and L3b are all equal.

[0052] The IDT electrode 4 includes a step portion 31a, a step portion 31b, a step portion 32a, and a step portion 32b. Step portion 31a is located between the first step portion 21a and the adjacent second step portion 22a. Step portion 31a forms a step along the direction from the first busbar 11a to the second busbar 11b, extending from the first step portion 21a to the second step portion 22a. Step portion 31b is located between the step portion 21b and the adjacent step portion 22b. Step portion 31b forms a step along the direction from the first busbar 11a to the second busbar 11b, extending from the step portion 21b to the step portion 22b. The step portion 32a is provided between the second step portion 22a and the adjacent third step portion 23a, and forms a step along the second step portion 22a toward the third step portion 23a in the direction from the first busbar 11a toward the second busbar 11b.

[0053] The step portion 32b is provided between the step portion 22b and the adjacent step portion 23b, and forms a step along the direction from the step portion 22b to the step portion 23b in the direction from the first busbar 11a toward the second busbar 11b.

[0054] These stepped sections 31a, 31b, 32a, and 32b are all formed along a direction from the first busbar 11a to the second busbar 11b, which is perpendicular to the propagation direction X of the elastic surface wave. The stepped sections are arranged alternately, forming an overall stepped structure.

[0055] Furthermore, when describing embodiments of the present invention, "step" refers to the distance between adjacent steps in the extending direction of the electrode (i.e., the direction from the first busbar to the second busbar).

[0056] In IDT electrode 4, the electrode finger 12a on the side of the first busbar 11a and the electrode finger 12b on the side of the second busbar 11b have the same length. The dummy electrodes 15a and 15b also have the same length. For gaps 17a and 17b, the distance between them and their nearest step is the same. The opening length of IDT electrode 4 (the length of the intersection region in the direction of the electrode finger) is the same in all regions of the first flat region 51, the second flat region 52, and the third flat region 53.

[0057] <Regarding the effect> In the elastic wave device with the above-described structure, the suppression effect on transverse modes is explained. To verify the effect of the elastic wave device 1 of this embodiment, multiple elastic wave devices with different stepped portions (including the SAW resonator in the comparative example and the embodiment) were fabricated and measured.

[0058] Figure 3(a) shows the relationship between the frequency and the real part of the admittance (conductance) Re(Y) of the elastic wave device of Example 1, with a step height of 1.0λ for the stepped portions 31a, 31b, 32a, and 32b. Figure 3(b) shows the relationship between the frequency and the real part of the admittance Re(Y) of the elastic wave device of Example 2, with a step height of 0.5λ for the stepped portion. Figure 3(c) shows a graph of the relationship between the frequency and the real part of the admittance Re(Y) of a comparative elastic wave device, excluding the stepped portions. Figure 4 The graphs above show the superposition of the three frequency characteristics. In these graphs, the horizontal axis represents frequency (in MHz), and the vertical axis represents the real part of admittance Re(Y) (in dB). Furthermore, to magnify the portion of the real admittance Re(Y) less than -30 dB, the portion exceeding -30 dB is not displayed.

[0059] Figure 5 This is a plan view of the IDT electrode 4X and reflector 5X of a comparative elastic wave device. (See attached diagram.) Figure 5 As shown, no steps are provided in the IDT electrode 4X.

[0060] The following lists the common conditions of the comparative examples, Example 1, and Example 2.

[0061] Wavelength λ: 4.1 μm Piezoelectric substrate 3: Material: 42° rotary Y-cut X-propagation lithium tantalate substrate Thickness: 0.27λ.

[0062] Intermediate layer 6: Material: SiO2 Thickness: 0.61λ Support substrate 2: Material: Spinel Thickness: 97.6λ IDT electrode refers to: IDT film structure: It consists of a bottom Ti film (130 nm), a middle AlCu film (268 nm), and a top Ti film (15 nm). Pitch: 0.5λ Duty cycle: 46% Electrode finger pairs: 114 Opening length: 17.5λ Virtual electrode length: 0.5λ Gap: 0.45 μm Number of reflector pairs: 10 like Figure 4 As shown, especially from the circled section, the contrast with the stepless section represented by the dashed line (in) is evident. Figure 4 Compared to Example 2 (represented by the dashed line, with a step height of 0.5λ), the real admittance peak value is smaller, indicating that transverse modes are suppressed. Furthermore, compared to Example 2 with a step height of 0.5λ, Example 1 with a step height of 1.0λ (represented by the solid line) has a smaller real admittance peak value, indicating that transverse modes are further suppressed. Therefore, since the elastic wave device of the first embodiment is provided with step portions 31a, 31b, 32a, and 32b, the transverse modes of the elastic wave device can be effectively suppressed.

[0063] like Figure 6 As shown, the solid line represents Embodiment 3, where the step height of the stepped portions 31a, 31b, 32a, and 32b is set to 1.5λ. This figure illustrates the real admittance of the elastic wave device at different frequencies. The dashed line represents the real admittance of the elastic wave device without stepped portions at different frequencies.

[0064] As can be seen from the figure, the real part of the admittance increases, particularly in the frequency band from the anti-resonance frequency Fa (approximately 942 MHz) to 980 MHz. Since this increase in the real part of the admittance in this frequency range means that it cannot adequately shield surface elastic waves when used as a filter, this phenomenon is undesirable. Furthermore, the real part of the admittance in the 942 MHz to 980 MHz band shows an increasing trend with increasing step height. Therefore, the step height should preferably be less than 1.5λ. Additionally, in the IDT electrode 4, if the total step height is too large, it will lead to increased energy loss, which is also undesirable. Specifically, the total step height of step portion 31a and step portion 32a (i.e., the distance from virtual line L1a to virtual line L3a) should preferably be less than 2.0λ. Similarly, the total step height of step portion 31b and step portion 32b (i.e., the distance from virtual line L1b to virtual line L3b) should preferably be less than 2.0λ.

[0065] <Second Implementation> Figure 7 This is a plan view of the IDT electrode 4A of the elastic wave device according to the second embodiment. In the following description, the reference numerals for parts with the same names and functions as in the previous embodiments will remain consistent, and repeated descriptions will be omitted. In this second embodiment, the IDT electrode 4A is composed of two segments: a first flat region 54 and a second flat region 55. On the first busbar 11a, a step portion 33a is formed between the first step portion 24a and the adjacent second step portion 25a. On the second busbar 11b, a step portion 33b is formed between the first step portion 24b and the adjacent second step portion 25b.

[0066] The first step 24a is located at the position of virtual line La1, and the second step 25a is located at the position of virtual line La2. The first step 24b is located at the position of virtual line Lb1, and the second step 25b is located at the position of virtual line Lb2.

[0067] As described above, in the elastic wave device employing the two-stage IDT electrode 4A, transverse modes can be suppressed. To verify the effectiveness of the elastic wave device 1 of this embodiment, multiple elastic wave devices (including the comparative example and the SAW resonator in the embodiment) with different step heights were fabricated and measured.

[0068] Figure 8a Example 4 is shown. Figure 7 The relationship between frequency and real admittance Re(Y) is shown when the step height of the step portion 33a and step portion 33b of the IDT electrode 4A is set to 1.0λ. Figure 8b Example 5 is shown. Figure 7The relationship between frequency and real admittance Re(Y) is shown when the step height of the step portion 33a and step portion 33b of the IDT electrode 4A is set to 0.5λ. Figure 8c The comparative example shows the use of a stepless IDT electrode (see [reference]). Figure 5 The relationship between the frequency and the real part of the admittance Re(Y) of an elastic wave device. Figure 9 This is a comparison chart showing the superposition of the three frequency characteristics mentioned above. The fabrication and measurement conditions are the same as those in Examples 1, 2, and 3 above.

[0069] like Figure 9 As shown, particularly from the portion marked with a broken circle, it can be seen that, compared to the comparative example without a step, Example 5 with a step height of 0.5λ has a smaller real admittance peak value, thus suppressing transverse modes. Furthermore, compared to Example 5 with a step height of 0.5λ, Example 4 with a step height of 1.0λ has a smaller real admittance peak value, thus further suppressing transverse modes. Therefore, since the IDT electrode 4A of the elastic wave device in the second embodiment has stepped portions 31a, 31b, 32a, and 32b, the transverse modes of the elastic wave device can be effectively suppressed. Thus, it can be seen that as long as the IDT electrode has a step, the transverse modes of the elastic wave device can be suppressed.

[0070] <Third Implementation> The IDT electrode 4B of the elastic wave device in the third embodiment is as follows: Figure 10 As shown. Figure 10 As shown, the IDT electrode adopts a three-segment structure. In the figure, from the first flat region 61 to the second flat region 62, steps 31a and 31b are formed downward (i.e., on the side of the second busbar 11b); from the second flat region 62 to the third flat region 63, steps 32a and 32b are formed upward (i.e., on the side of the first busbar 11a).

[0071] Because the stepped portions 31a, 31b, 35a, and 35b are provided in the elastic wave device, the transverse mode can be effectively suppressed.

[0072] <Fourth Implementation> A plan view of the IDT electrode 4C of the elastic wave device in the fourth embodiment is shown below. Figure 11 As shown. Figure 11 As shown, the IDT electrode 4C includes a first flat region 81, a second flat region 82, a third flat region 83, and a ramp region 91 and a ramp region 92, which are regions with inclined steps.

[0073] In IDT electrode 4C, such as Figure 11As shown, from the first flat region 81 to the second flat region 82, the flow gradually descends downwards through the slope region 91 (i.e., from the first confluence bar 11a toward the second confluence bar 11b), while from the second flat region 82 to the third flat region 83, the flow gradually ascends upwards through the slope region 92 (i.e., from the second confluence bar 11b toward the first confluence bar 11a).

[0074] Sloping regions 91 and 92 refer to the areas where the bases 18a, 18b, and 18c of the electrode fingers or the bases 19a, 19b, and 19c of the dummy electrodes are arranged along the inclined virtual lines S1a, S1b, S2a, and S2b. In sloping regions 91 and 92, because the bases 18a, 18b, and 18c of the electrode fingers or the bases 19a, 19b, and 19c of the dummy electrodes are adjacent to each other at the positions of the inclined virtual lines S1a, S1b, S2a, and S2b, inclined stepped portions (sloping portions) are formed. This sloping structure is formed by the arrangement of these bases.

[0075] On the virtual line S1a in the slope region 91, the bases 19a, 19b, and 19c of the dummy electrode 15b are provided. In the extension direction of the electrode finger, the base 19a is located at the position of the step 71a (virtual line M1a), the base 19b is located at the position of the step 72a (virtual line M2a), and the base 19c is located between the virtual lines M1a and M2a.

[0076] On the virtual line S1b of the slope region 91, bases 18a, 18b, and 18c of electrode finger 12b are provided. In the extension direction of the electrode finger, base 18a is located at the position of step 71b (virtual line M1b), base 18b is located at the position of step 72b (virtual line M2b), and base 18c is located between virtual lines M1b and M2b.

[0077] In the slope region 91, since at least one base 18c or base 19c is provided between the step portions 37a or 37b, the adjacent bases are arranged at an angle, thereby forming a slope structure and a slope region. In this embodiment, only one base is provided between the step portions 37a or 37b on each virtual line (S1a or S1b), but multiple bases may also be provided.

[0078] On the virtual line S2a of the slope region 92, the bases 18a, 18b, and 18c of the electrode fingers 12a are provided. In the extension direction of the electrode fingers, the base 18a is located at the position of the step 72a (virtual line M2a), the base 18b is located at the position of the step 73a (virtual line M1a), and the base 18c is located between the virtual lines M1a and M2a.

[0079] On the virtual line S2b of the slope region 92, the bases 19a, 19b, and 19c of the virtual electrode 15b are provided. In the extension direction of the electrode finger, the base 19a is located at the position of the step 72b (virtual line M2b), the base 19b is located at the position of the step 73b (virtual line M1b), and the base 19c is located between the virtual lines M1b and M2b.

[0080] In the slope region 92, since at least one base 18c or base 19c is provided between the step portions 37a or 37b, the adjacent bases are arranged at an angle, thereby forming a slope structure and a slope region. In this embodiment, only one base is provided between the step portions 37a or 37b on each virtual line (S2a or S2b), but multiple bases may also be provided.

[0081] On the first busbar 11a, there is a flat portion parallel to the X direction, including a first step 71a, a second step 72a, and a third step 73a. The first step 71a and the third step 73a are located at the position of virtual line M1a, and the second step 72a is located at the position of virtual line M2a. The distance between virtual lines M1a and M2a is the height of the step 37a (i.e.,...). Figure 11 (The vertical spacing shown).

[0082] On the second busbar 11b, there are a first step 71b, a second step 72b, and a third step 73b. The first step 71b and the third step 73b are located at the position of virtual line M1b, and the second step 72b is located at the position of virtual line M2b. The distance between virtual lines M1a and M2a is the height of step 37b (i.e.,...). Figure 11 (The vertical spacing shown).

[0083] As described above, in the IDT electrode 4C, since steps 37a and 37b are provided between adjacent stepped portions along the direction from the first busbar to the second busbar (perpendicular to the elastic surface wave propagation direction X) through ramp regions 91 and 92, the transverse mode of the elastic wave device can be effectively suppressed. Furthermore, this embodiment employs a ramp-shaped step with bases 18b and 19c provided between steps 37a and 37b, which can more effectively improve the Q value compared to the non-rammed step structure used in the first to third embodiments. Additionally, in this embodiment, the steps 37a and 37b in ramp regions 91 and 92 have the same height, but they can also be set to different heights. Similar to the first embodiment, the step width in the electrode finger extension direction is preferably less than 1.5λ, and the total step height of steps 37a and 38a (i.e., the distance from virtual line M1a to virtual line M3a) and the total step height of steps 37b and 38b (i.e., the distance from virtual line M1b to virtual line M3b) are both preferably less than 2.0λ.

[0084] The widths of ramp regions 91 and 92 in the X direction are explained below. The widths of ramp regions 91 and 92 in the X direction are shorter than those of the first step 71b, the second step 72b, and the third step 73b. By setting the widths of ramp regions 91 and 92 to be shorter than those of the flat regions 71b, 72b, and 73b, the peak values ​​of the high-frequency regions (similar to...) Figure 9 The peak at approximately 988 MHz, which is also expected to appear on the frequency-admittance real part curve in this embodiment, may shift towards the resonant frequency side (e.g., Figure 9 The frequency response is shifted to around 910 MHz (the low-frequency side) to prevent this phenomenon from occurring and maintain good frequency characteristics.

[0085] In the IDT electrode 4C, the electrode finger 12a on the side of the first busbar 11a and the electrode finger 12b on the side of the second busbar 11b have the same length. The dummy electrodes 15a and 15b also have the same length. For gaps 17a and 17b, the distance between them and the electrode finger base 18 is basically the same in their respective nearest adjacent step or ramp regions. The opening length of the IDT electrode 4 (the length of the cross region in the direction of the electrode finger) is basically consistent in all regions (first flat region 81, second flat region 82, third flat region 83, ramp region 91, and ramp region 92). Furthermore, in ramp regions 91 and 92, gaps 17a and 17b are also arranged in a continuous, sloping pattern.

[0086] <Fifth Implementation> A plan view of the IDT electrode 4D of the elastic wave device in the fifth embodiment is shown below. Figure 12 As shown. Figure 12 As shown, the IDT electrode 4D includes a first flat region 81, a second flat region 82, a third flat region 84, and ramp regions 91 and 93, which are regions with inclined steps. In the IDT electrode 4D, from the first flat region 81 to the second flat region 82, through the ramp region 91, along... Figure 12 The downward direction shown (i.e., from the first busbar 11a towards the second busbar 11b) gradually decreases; from the second flat region 82 to the third flat region 84, it decreases further downward through the ramp region 93. Ramp regions 91 and 93 refer to the regions where the bases 18a, 18b, and 18c of electrode fingers 12a or 12b, or the bases 19a, 19b, and 19c of dummy electrodes, are arranged along inclined virtual lines S1a, S1b, S3a, and S3b. These virtual lines are inclined relative to both the extension direction of the electrode fingers and the propagation direction of the elastic surface wave.

[0087] In the slope region 91, the bases 19a, 19b, and 19c of the dummy electrode 15a are arranged in a slope-like manner along the inclined dummy line S1a. In the extension direction of the electrode finger, base 19a is located at the position of step 71a (the position of dummy line M1a), base 19b is located at the position of step 72a (the position of dummy line M2a), and base 19c is located between dummy lines M1a and M2a.

[0088] In the slope region 91, the bases 18a, 18b, and 18c of the electrode fingers 12b are arranged in a slope-like manner along the inclined virtual line S1b. In the extension direction of the electrode fingers, the base 18a is located at the position of the step portion 71b (the position of the virtual line M1b), the base 18b is located at the position of the step portion 72b (the position of the virtual line M2b), and the base 18c is located between the virtual lines M1b and M2b.

[0089] In the slope region 93, the bases 18a, 18b, and 18c of the electrode fingers 12a are arranged in a slope-like manner along the inclined virtual line S3a. In the extension direction of the electrode fingers, the base 18a is located at the position of the stepped portion 72a (the position of the virtual line M2a), the base 18b is located at the position of the stepped portion 74a (the position of the virtual line M3a), and the base 18c is located between the virtual lines M2a and M3a.

[0090] In the slope region 93, the bases 19a, 19b, and 19c of the dummy electrode 15b are arranged in a slope-like manner along the inclined dummy line S3b. In the extension direction of the electrode finger, base 19a is located at the position of step 72b (the position of dummy line M2b), base 19b is located at the position of step 74b (the position of dummy line M3b), and base 19c is located between dummy lines M2b and M3b.

[0091] On the first busbar 11a, there are a first step 71a, a second step 72a, and a third step 74a. The first step 71a is located at the position of virtual line M1a, the second step 72a is located at the position of virtual line M2a, and the third step 74a is located at the position of virtual line M3a. The spacing between virtual lines M1a and M2a corresponds to the height of the step 37a (i.e., Figure 12 The vertical spacing in the middle), the spacing between the virtual lines M2a and M3a corresponds to the height of the step 38a.

[0092] On the second busbar 11b, there are a first step 71b, a second step 72b, and a third step 74b. The first step 71b is located at the position of virtual line M1b, the second step 72b is located at the position of virtual line M2b, and the third step 74b is located at the position of virtual line M3b. The spacing between virtual lines M1b and M2b corresponds to the height of the step 37b (i.e., Figure 12 The vertical spacing in the middle), the spacing between virtual lines M2b and M3b corresponds to the height of step 38b.

[0093] The IDT electrode 4D, through the ramp regions 91 and 93, forms steps 37a, 37b, 38a, and 38b in the extension direction of the electrode finger (i.e., the direction perpendicular to the propagation direction X of the elastic surface wave), thereby effectively suppressing the transverse mode of the elastic wave device.

[0094] Figure 13 This is a magnified view of a portion of the IDT electrode 4D. Regarding the location of the electrode base 18c, as shown... Figure 13 As shown, in the extension direction of the electrode finger (the direction perpendicular to direction X), if there is a deviation in the left and right positions of the electrode finger root (i.e., the intersection of the cross-region side end 100 and cross-region side end 101 of the busbar 11b with the outline of the electrode finger 12b), then the electrode finger base 18c should be located between these positions (i.e., Figure 13 (Near the area marked by the dashed box). For the base of other electrodes and the base of dummy electrodes, if there is a deviation in the position of their left and right roots, the same treatment should be applied.

[0095] <Sixth Implementation Method> A plan view of the IDT electrode 4E of the elastic wave device in the sixth embodiment is shown below. Figure 14 As shown. Figure 14 As shown, the IDT electrode 4E of this embodiment does not have a dummy electrode. In the IDT electrode 4E, at the position corresponding to the base of the dummy electrode in the aforementioned embodiment, the cross-regional end 20 of the busbars 11a and 11b is arranged in a sloped shape along the inclined dummy lines S4b and S5a. Furthermore, the base 18 of the electrode fingers is arranged in a sloped shape along the dummy lines S4a and S5b. The IDT electrode 4E includes a first flat region 86, a second flat region 87, a third flat region 88, and sloped regions 95 and 96, which are regions with inclined stepped portions. In the IDT electrode 4E, from the first flat region 86 to the second flat region 87, through the sloped region 95, along... Figure 14 It rises in the upward direction shown (i.e., from the second confluence bar 11b to the first confluence bar 11a); it descends from the second flat region 87 to the third flat region 88 through the slope region 96.

[0096] As described above, the IDT electrode 4E, through the ramp regions 95 and 96, forms steps 39a and 39b in the extension direction of the electrode finger (i.e., the direction perpendicular to the propagation direction X of the elastic surface wave), thereby effectively suppressing the transverse mode of the elastic wave device.

[0097] In the above embodiments, the relative positions of the first busbar 11a and the second busbar 11b can also be interchanged. Furthermore, the present invention is also applicable to elastic wave devices without dummy electrodes 15a and 15b, and elastic wave devices without reflector 5.

[0098] It should be noted that the illustrations used in the above description are for illustrative purposes only, and the dimensions and proportions in the illustrations may not be exactly the same as the actual product.

[0099] The present invention has been described above. However, as an elastic wave device, the specific implementation of the present invention is not limited to the above embodiments in practical applications. Various changes and additional modifications can be made without departing from the core technical concept of the present invention.

[0100] Although several aspects of some embodiments have been described, it should be understood that various modifications, improvements, and enhancements will readily occur to those skilled in the art. These modifications, improvements, and enhancements are intended to be part of this invention and are within the scope of this disclosure.

[0101] The specific implementation examples are provided for illustrative purposes only and are not intended to be limiting.

[0102] The expressions and terms used in this disclosure are for illustrative purposes and should not be construed as limiting. The terms “containing,” “including,” “having,” “comprising,” and variations thereof, as used herein, are intended to include the following items and their equivalents and additional items.

[0103] The reference to “or” is intended to be understood as any term used may refer to one, more or all of the terms mentioned.

[0104] The references to directions such as front, back, left, right, top, bottom, up, down, horizontal, vertical, inside, etc., are all for the convenience of description. These references do not limit the constituent elements of the present invention to any particular location or spatial orientation. Therefore, the above descriptions and illustrations are merely examples.

Claims

1. An elastic wave device, characterized in that, include: piezoelectric layer; IDT electrodes formed on the piezoelectric layer; The IDT electrode includes a first busbar and a second busbar that are opposite to each other; In the top view, the first busbar and the second busbar are provided with a plurality of stepped portions parallel to the direction of propagation of the elastic surface wave on the side of the first busbar and the second busbar facing each other, and the stepped portions adjacent to each other are located at different positions along the direction from the first busbar to the second busbar. A step is provided between adjacent stepped sections; In the top view, the stepped portion of the first busbar and the stepped portion of the second busbar are equidistant from each other.

2. The elastic wave device according to claim 1, characterized in that, The elastic wave device is an elastic surface wave device. When the wavelength of the elastic surface wave is λ, the width of the step portion perpendicular to the propagation direction of the elastic surface wave is less than 1.5λ.

3. The elastic wave device according to claim 1, characterized in that, The first busbar and the second busbar each comprise three stepped portions: a first stepped portion, a second stepped portion adjacent to the first stepped portion, and a third stepped portion adjacent to the second stepped portion. A step is provided between the first step and the second step, and the step is formed along the direction from the first busbar toward the second busbar. A step is provided between the second step and the third step, and the step is formed along the direction from the second step to the third step, in the direction from the second busbar to the first busbar.

4. The elastic wave device according to claim 1, characterized in that, The first busbar and the second busbar each include: a first step portion, a second step portion adjacent to the first step portion, a step portion disposed between the first step portion and the second step portion, a third step portion adjacent to the second step portion, and a step portion disposed between the second step portion and the third step portion; As the first step, the second step, and the third step change in sequence, steps are formed in the same direction, and the direction of the step is: from the second busbar toward the first busbar, or from the first busbar toward the second busbar.

5. The elastic wave device according to claim 1, characterized in that, In the top view, the first busbar and the second busbar are provided with a plurality of stepped portions parallel to the direction of propagation of the elastic surface wave on opposite sides, and a step portion is provided between adjacent stepped portions. When the wavelength of the elastic wave is λ, the total height of the step portion in the direction from the first busbar to the second busbar is less than 2.0λ.

6. The elastic wave device according to claim 1, characterized in that, In the top view, the first busbar and the second busbar are provided with a plurality of stepped portions parallel to the direction of propagation of the elastic surface wave on opposite sides, and a step portion is provided between adjacent stepped portions, the step portion being formed in a direction perpendicular to the direction of propagation of the elastic surface wave.

7. The elastic wave device according to claim 1, characterized in that, In the top view, the first busbar and the second busbar have multiple stepped portions parallel to the direction of elastic surface wave propagation on opposite sides, and a step portion is provided between adjacent stepped portions. One side has multiple ends arranged along an inclined virtual line, which is inclined to the direction of elastic wave propagation.

8. The elastic wave device according to claim 1, characterized in that: In the top view of the IDT electrode, the first busbar and the second busbar respectively include a first flat region, a second flat region, a third flat region, and a sloping region disposed between adjacent flat regions.

9. The elastic wave device according to claim 8, characterized in that: The IDT electrode further includes a plurality of electrode fingers extending from the first bus bar to the second bus bar, a plurality of electrode fingers extending from the second bus bar to the first bus bar, and dummy electrodes respectively facing the electrode fingers. A gap is formed between the end of the electrode fingers and the dummy electrodes. The slope region is the region where the base of the electrode fingers or the base of the dummy electrodes are arranged along an inclined virtual line.

10. The elastic wave device according to claim 9, characterized in that: The slope region serves as a step between adjacent stepped sections. Each stepped section is provided with at least one base of an electrode finger or a base of a dummy electrode, such that the bases of adjacent electrode fingers or adjacent dummy electrodes are arranged at an angle to form a slope structure and thus the slope region.

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