Elastic wave device, splitter and communication device

Abstract

There is a demand for reducing spurious signals in acoustic wave devices. [Solution] An elastic wave device comprises a substrate having an end face and a piezoelectric body, and a plurality of strip electrodes located above the substrate and each extending parallel to the substrate, at least some of the plurality of strip electrodes are excitation sections capable of exciting elastic waves, the end face is parallel to the extension direction of the strip electrodes in a planar view from above and is located in the elastic wave propagation direction relative to the excitation section, the plurality of strip electrodes include a first strip electrode located furthest from the end face in the elastic wave propagation direction, and a second strip electrode which is the excitation section and is farther from the end face than the first strip electrode in the elastic wave propagation direction, in a cross section cut in the elastic wave propagation direction, the average thickness of the first strip electrode is smaller than the average thickness of the second strip electrode, the substrate has a groove on its upper surface, and the end face is part of the side surface of the groove.

Description

[Technical field]

[0001] The present disclosure relates to an acoustic wave device that utilizes acoustic waves, a method for manufacturing the acoustic wave device, a duplexer including the acoustic wave device, and a communication device including the duplexer. [Background technology]

[0002] Acoustic wave devices that utilize acoustic waves are known. An example of an acoustic wave device is a SAW (Surface Acoustic Wave) device. An acoustic wave device has a structure that reflects propagating acoustic waves. The surface acoustic wave device disclosed in Patent Document 1 is an end face reflection type surface acoustic wave device that has an end face as a reflection structure. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2018 / 096783A1 Summary of the Invention [Problem to be solved by the invention]

[0004] There is a demand for reducing spurious signals in acoustic wave devices. [Means for solving the problem]

[0005] An elastic wave device according to the present disclosure comprises a substrate having an end face and a piezoelectric body, and a plurality of strip electrodes located above the substrate and extending parallel to each other, at least some of the plurality of strip electrodes are excitation sections capable of exciting elastic waves, the end face is parallel to the extension direction of the strip electrodes in a planar view from above and is located in an elastic wave propagation direction relative to the excitation section, the plurality of strip electrodes include a first strip electrode located closest to the end face in the elastic wave propagation direction, and a second strip electrode which is the excitation section and is farther from the end face than the first strip electrode in the elastic wave propagation direction, and in a cross section cut in the elastic wave propagation direction, the average thickness of the first strip electrode is smaller than the average thickness of the second strip electrode, the substrate has a groove on its upper surface, and the end face is part of a side surface of the groove. Effect of the Invention

[0006] According to one aspect of the present disclosure, it is possible to reduce spurious signals in an acoustic wave device. [Brief description of the drawings]

[0007] [Figure 1] FIG. 1 is a schematic plan view of an elastic wave device according to an embodiment of the present disclosure. [Diagram 2] FIG. 1 is a schematic cross-sectional view of an elastic wave device according to an embodiment of the present disclosure. [Figure 3A] FIG. 1 is a schematic cross-sectional view of an elastic wave device according to an embodiment of the present disclosure. [Figure 3B] FIG. 1 is a schematic cross-sectional view of an elastic wave device according to an embodiment of the present disclosure. [Figure 3C] FIG. 1 is a schematic cross-sectional view of an elastic wave device according to an embodiment of the present disclosure. [Figure 4A] FIG. 1 is a schematic plan view of an elastic wave device according to an embodiment of the present disclosure. [Figure 4B] FIG. 1 is a schematic plan view of an elastic wave device according to an embodiment of the present disclosure. [Diagram 5] FIG. 1 is a schematic plan view of an elastic wave device according to an embodiment of the present disclosure. [Figure 6] FIG. 1 is a schematic cross-sectional view of an elastic wave device according to an embodiment of the present disclosure. [Figure 7] 1A to 1C are schematic cross-sectional views illustrating a manufacturing method of an elastic wave device according to an embodiment of the present disclosure. [Figure 8] FIG. 2 is a schematic circuit diagram of a duplexer according to an embodiment of the present disclosure. [Figure 9] FIG. 2 is a schematic circuit diagram of a communication device according to an embodiment of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] Hereinafter, embodiments and comparative examples according to the present disclosure will be described with reference to the drawings. The drawings used in the following description are schematic, and the dimensional ratios and the like in the drawings do not necessarily correspond to the actual ones. Furthermore, the dimensional ratios of the drawings do not necessarily correspond to each other.

[0009] In this disclosure, an orthogonal coordinate system represented by the D1 axis, the D2 axis, and the D3 axis is attached to the drawings. The D2 axis is an axis parallel to the direction in which the excitation unit 311 described later extends from the second bus bar 351b described later. The D1 axis is an axis perpendicular to the D2 axis in the plane of the substrate 2. The D3 axis is an axis perpendicular to the upper surface of the piezoelectric body 21. In other words, the D3 axis is the stacking direction of the substrate 2. In this disclosure, the positive direction of the D1 axis is a direction from the excitation unit 311 described later to one end face 41 described later. In this disclosure, the positive direction of the D1 axis is also described as the elastic wave propagation direction. In this disclosure, the negative direction of the D1 axis is also described as the opposite direction to the elastic wave propagation direction. The end face 41 may be located in both directions of the D1 axis with respect to the excitation unit 311, but for the sake of explanation, in this disclosure, the direction from the excitation unit 311 to one end face 41 is considered to be the elastic wave propagation direction. Here, the elastic wave excited by the excitation unit 311 may be a surface acoustic wave or a plate wave. The positive direction of the D2 axis is the direction in which the second excitation unit 311b described later extends from the second bus bar 351b described later. The positive direction of the D3 axis is the direction from the substrate 2 described later toward the electrode layer 3 described later. Furthermore, when referring to a planar surface or planar view, unless otherwise specified, this refers to a view from above with respect to the D3 axis. For example, when referring to a planar view from above, this refers to a view from above with respect to the D3 axis.

[0010] In the elastic wave device 1 according to the present disclosure, either direction may be considered to be the upper or lower direction, but for convenience, the positive direction of the D3 axis may be considered to be the upper direction, and terms such as the upper surface and the lower surface may be used.

[0011] Furthermore, although the thickness of a layer may be mentioned in this disclosure, unless otherwise specified, it may be considered at the thickest portion or the thinnest portion in any cross section.

[0012] The following are embodiments of the present disclosure. The configurations described in the following embodiments may be freely combined with any of the other embodiments.

[0013] [First embodiment] A first embodiment of an elastic wave device 1 according to the present disclosure will be described. Fig. 1 is a schematic plan view of elastic wave device 1. Elastic wave device 1 includes a substrate 2, an electrode layer 3 located above substrate 2, and an end face 41 included in substrate 2. Fig. 2 is a schematic cross-sectional view of elastic wave device 1.

[0014] (substrate) The substrate 2 has a piezoelectric body 21. The substrate 2 may have a first layer 22 and / or a support substrate 23 located below the piezoelectric body 21, as shown in FIG.

[0015] The piezoelectric body 21 is made of lithium niobate (LiNbO 3 : hereafter referred to as LN) or lithium tantalate (LiTaO 3 For example, the piezoelectric body 21 may be made of a 36 to 54° Y-cut X-propagation LT layer.

[0016] The first layer 22 can be made of, for example, silicon dioxide (SiO 2 ). The first layer 22 reduces surface waves leaking downward from the piezoelectric body 21, and can reduce the insertion loss of the acoustic wave device 1.

[0017] The support substrate 23 supports the electrode layer 3 and the piezoelectric body 21, and improves the strength of the substrate 2. When the support substrate 23 is provided, the first layer 22 improves the bonding strength between the piezoelectric body 21 and the support substrate 23.

[0018] (end face) As shown in Fig. 1, the substrate 2 includes an end face 41. One end face 41 is located in the elastic wave propagation direction relative to the excitation section 311 described below. The end face 41 may be located in both directions of the D1 axis relative to the excitation section 311. The end face 41 reflects the elastic wave as a reflected wave in the negative direction of the D1 axis. In other words, the end face 41 is a reflecting structure.

[0019] The end surface 41 may be a part of the groove portion 4. Specifically, as shown in Fig. 1, a part of the side surface of the groove portion 4 may be the end surface 41. In this case, both side surfaces of the groove portion 4 can be used as the end surface 41.

[0020] In a plan view, end surface 41 is positioned parallel to the extension direction of strip electrode 31. Here, "parallel" may include a margin of error within a range that does not significantly affect the specific characteristics of acoustic wave device 1.

[0021] In the present disclosure, an "end face" is defined as a surface that reflects an acoustic wave. For example, the end face may be the surface at the end of a substrate or the inner wall surface of a groove in the substrate.

[0022] (electrode layer) The electrode layer 3 is formed so as to be in direct or indirect contact with the upper surface of the piezoelectric body 21. Although not particularly shown, a base layer may be located between the electrode layer 3 and the piezoelectric body 21. The base layer can improve the adhesive strength between the electrode layer 3 and the piezoelectric body 21. Examples of materials for the base layer include titanium (Ti), chromium (Cr), various dielectrics, etc.

[0023] The electrode layer 3 is made of a material having electrical conductivity. For example, various conductive materials such as aluminum (Al), copper (Cu), platinum (Pt), molybdenum (Mo), gold (Au), titanium (Ti), or alloys of these can be used as the material for the electrode layer 3. Furthermore, the electrode layer 3 may be made by stacking a plurality of these layers. Although not shown, the electrode layer 3 may have a stacked structure that combines the above materials. For example, Al and CuAl 2 A laminated structure of LT and Al or a laminated structure of Al and Ti may be used. The etching selectivity of LT and Al is lower than that of LT and Pt, Mo, Au or Ti. Therefore, when an electrode layer 3 containing Al as a main component is used, it is easy to thin the layer by etching, and it is easy to form the first strip electrode 315 described later. In the present disclosure, the main component may be a substance that occupies the largest proportion by weight or molar ratio, or a substance that occupies more than half of the total thickness in the D3 axis in a cross section cut in the elastic wave propagation direction.

[0024] 1, the electrode layer 3 has a plurality of strip electrodes 31. In the present disclosure, a strip electrode 31 refers to one of a group of thin electrodes extending parallel to the D2 axis. The plurality of strip electrodes 31 extend parallel to each other. The number of the plurality of strip electrodes 31 may be set appropriately depending on the electrical characteristics required of the acoustic wave device 1. The number may be more or less than the number shown in the schematic cross-sectional view and plan view according to the present disclosure.

[0025] At least some of the strip electrodes 31 are excitation sections 311 capable of exciting an acoustic wave. For example, as shown in Fig. 1, the excitation sections 311 may be included in an IDT electrode 35. The IDT electrode 35, which is configured by the excitation sections 311 and a bus bar 351, can excite an acoustic wave.

[0026] When the acoustic wave device 1 has an IDT electrode 35, the IDT electrode 35 includes an excitation portion 311 and a bus bar 351. Here, the bus bar 351 refers to a portion that electrically connects the strip electrodes 31 that are the excitation portion 311. The IDT electrode 35 has, as the bus bar 351, a first bus bar 351a and a second bus bar 351b that are not electrically connected to each other and face each other. The excitation portion 311 has a first excitation portion 311a extending from the first bus bar 351a toward the second bus bar 351b, and a second excitation portion 311b extending from the second bus bar 351b toward the first bus bar 351a.

[0027] The lengths of the excitation parts 311 are, for example, equal to each other. The IDT electrode 35 may be apodized, in which the length of the excitation part 311 changes depending on the position in the propagation direction. Apodization can make the elastic wave propagating as the main resonance more dominant.

[0028] Although not particularly shown, IDT electrode 35 may have dummy electrode fingers extending from bus bar 351 toward the opposing bus bar 351. The dummy electrode fingers may be shorter in the D2 axis compared with excitation portions 311. IDT electrode 35 may have a variable width between excitation portions 311 or may be inclined with respect to the D1 axis.

[0029] The multiple strip electrodes 31 include a first strip electrode 315 located closest to the end face 41 in the acoustic wave propagation direction, and a second strip electrode 3117 located farther from the end face than the first strip electrode 315. Here, the second strip electrode 3117 is an excitation section 311. The second strip electrode 3117 may be any of the excitation sections 311 that excite the primary resonance of the acoustic wave device 1.

[0030] In the elastic wave device 1, the average thickness of the excitation section 311 in a cross section cut in the elastic wave propagation direction is appropriately adjusted to contribute to propagating the elastic wave in the positive direction of the D1 axis. In other words, the average thickness of the excitation section 311 may be determined for the propagation of the elastic wave. In this disclosure, unless otherwise specified, the term "average thickness" refers to the thickness in a cross section cut in the elastic wave propagation direction. In addition, in this disclosure, the average thickness of each strip electrode 31 may be determined by dividing the cross-sectional area of ​​the strip electrode 31 by the lower side of the strip electrode 31 in a cross section cut in the D1 axis of the elastic wave device 1, or may be determined by various other methods.

[0031] In elastic wave device 1 according to the first embodiment, the average thickness of first strip electrode 315 is smaller than the average thickness of second strip electrode 3117. As a result, the behavior of the propagating elastic wave changes between second strip electrode 3117, which is excitation section 311, and first strip electrode 315. A portion of the elastic wave energy that becomes spurious near first strip electrode 315 can be leaked downward. Furthermore, elastic wave device 1 utilizes the reflected wave reflected by end face 41. By leaking a portion of the spurious elastic wave energy of the reflected wave downward near end face 41 where the reflected wave is generated, the spurious of elastic wave device 1 can be reduced.

[0032] The average thickness of first strip electrode 315 may be appropriately adjusted to adjust specific characteristics. As described above, the small average thickness of first strip electrode 315 allows a portion of the spurious acoustic waves to leak downward, thereby reducing the spurious of the acoustic wave device 1. On the other hand, first strip electrode 315 allows a portion of the primary resonance acoustic waves to leak, thereby increasing loss in the acoustic wave device 1. For example, the average thickness of first strip electrode 315 may be adjusted to balance the loss and spurious of the acoustic wave device 1. For example, the average thickness of first strip electrode 315 may be adjusted to reduce the loss and spurious.

[0033] The average thickness of the majority of the strip electrodes 31 that are excitation sections 311 is the same as that of the second strip electrode 3117. This makes it possible to make the elastic wave excited as the main resonance of the elastic wave device 1 more dominant. In this disclosure, the average thickness being "the same" may include an error within a range that does not significantly affect specific characteristics of the elastic wave device 1. In this disclosure, "the majority of the strip electrodes 31 that are excitation sections 311" refers to the majority of the strip electrodes 31 that are excitation sections 311, including the second strip electrode 3117. For example, the average thickness of the strip electrodes 31 that are excitation sections 311 may be found, and the number of strip electrodes 31 that have the same average thickness as the second strip electrode 3117 may be counted.

[0034] The thickness of a portion of first strip electrode 315 may be thinned. For example, if first strip electrode 315 has a shape as shown in Figures 3A to 3C, spurious emissions can be further reduced. In this case, for example, it becomes easier to adjust the balance between loss and spurious emissions.

[0035] 3A to 3C, the first strip electrode 315 may have a part on the end face 41 side that is thinned. In other words, the first strip electrode 315 includes a first portion 315a and a second portion 315b that is thinner than the first portion 315a in a cross section cut in the elastic wave propagation direction, and the second portion 315b is located closer to the end face 41 than the first portion 315a in the elastic wave propagation direction.

[0036] 3A, the first strip electrode 315 may have a stepped shape in the negative direction of the D2 axis. In other words, the first strip electrode 315 may have a lower surface R, a first upper surface T1, a second upper surface T2 located closer to the end surface 41 than the first upper surface T1 in the acoustic wave propagation direction, and a riser surface K connecting the first upper surface T1 and the second upper surface T2, and the first upper surface T1 may be located higher than the second upper surface T2. In this case, a part of the acoustic wave that becomes a spurious sound propagates through the second upper surface T2 located on the lower side and is likely to leak downward. As a result, the spurious sound of the acoustic wave device 1 can be further reduced.

[0037] 3B, first strip electrode 315 may have a trapezoidal shape with an inclined upper surface. In other words, first strip electrode 315 has a lower surface R, a first surface S that is in contact with lower surface R and is located on the end surface 41 side in the acoustic wave propagation direction, and an upper surface T that is in contact with first surface S, and upper surface T may be inclined with respect to lower surface R. In this case, part of the acoustic waves that become spurious leaks downward along the inclined upper surface T. As a result, the spurious of acoustic wave device 1 can be further reduced.

[0038] 3C , the vertex portion on the side of end face 41 may be curved. In other words, first strip electrode 315 has a bottom face R, a first face S that is located on the side of end face 41 among the side faces that are in contact with bottom face R in the acoustic wave propagation direction, a top face T that is in contact with first face S, and a second face U that connects first face S and top face T, and second face U may be curved. In this case, part of the spurious acoustic waves leaks downward along second face U, which is a curved surface. As a result, the spurious of acoustic wave device 1 can be reduced.

[0039] 4A, the first strip electrode 315 may be a floating electrode 313 that is not electrically connected to the excitation section 311. This can reduce the effect of the first strip electrode 315, which has a small average thickness, on the excitation of the acoustic wave in the excitation section 311. In addition, the floating electrode 313 can adjust the sound speed of the excited acoustic wave and / or the reflected wave.

[0040] 4B, the electrode layer 3 may have a reflector 37. In this case, the first strip electrode 315 refers to the strip electrode 31 located closest to the end face 41 in the acoustic wave propagation direction, among the strip electrodes 31 included in the reflector 37.

[0041] The side surface of the first strip electrode 315 and the end surface 41 do not necessarily need to be continuous, but the side surface of the first strip electrode 315 may be continuous with the end surface 41 as shown in Fig. 1. In this case, the first strip electrode 315 and the end surface 41 can be formed by a single etching process.

[0042] The width of the D1 axis of first strip electrode 315 may be changed compared to the other strip electrodes 31. In this case, the mode of the reflected wave can be adjusted to reduce spurious emissions of the acoustic wave device 1. For example, as shown in FIG 5, the width of first strip electrode 315 in the acoustic wave propagation direction may be made larger than that of second strip electrode 3117. In this case, the possibility that second strip electrode 3117 will be etched is reduced in the manufacturing method described below.

[0043] [Second embodiment] A second embodiment according to the present disclosure will be described below. In the following, a description of parts common to the first embodiment will be omitted, and only different parts will be described.

[0044] (end face) 2 , the elastic wave device 1 in accordance with the second embodiment has an inclined end face 41. In other words, the angle α between an extension of the top surface of the piezoelectric body 21 and a tangent at any point on the end face 41 is smaller than 90°. The inclination of the end face 41 allows some of the spurious elastic waves to leak downward, thereby reducing the spurious emissions of the elastic wave device 1.

[0045] In this disclosure, when determining the angle formed by a "tangent" at any point on a straight line, the straight line is determined as the "tangent." The description "a tangent at any point on the end face" does not limit the end face to a curved surface or curved line.

[0046] Angle α may be set to an appropriate value to adjust a particular characteristic. As described above, end face 41 is inclined, thereby allowing a portion of the elastic wave that becomes a spurious to leak downward, thereby reducing the spurious of elastic wave device 1. On the other hand, end face 41 allows a portion of the elastic wave that becomes the main resonance to leak, thereby increasing the loss of elastic wave device 1. For example, angle α may be adjusted to balance the loss and spurious of elastic wave device 1. For example, angle α may be adjusted to reduce the loss and spurious. Elastic wave device 1 according to the second embodiment has first strip electrode 315 and end face 41 as a structure for reducing spurious, which makes it easy to adjust the balance between loss and spurious.

[0047] Furthermore, when the end face 41 is inclined, the distance on the D1 axis from the IDT electrode 35 to the end face 41 varies depending on the coordinate on the D2 axis. As a result, spurious signals are likely to occur due to the reflection of acoustic waves by the end face 41, and therefore the first strip electrode 315, which leaks acoustic wave energy near the end face 41, can further reduce the spurious signals. For example, when the angle α is smaller than 82°, spurious signals are particularly likely to occur near the end face 41, and therefore the first strip electrode 315 can further reduce the spurious signals.

[0048] [Third embodiment] A third embodiment according to the present disclosure will be described below. In the following, a description of parts common to the first embodiment will be omitted, and only different parts will be described.

[0049] (end face) As shown in Fig. 6, the end surface 41 includes a first end surface 41a and a second end surface 41b. The first end surface 41a is located on the upper surface side of the piezoelectric body 21, and the second end surface 41b is located on the lower surface side of the piezoelectric body 21. As shown in Fig. 6, the first end surface 41a is inclined more steeply than the second end surface 41b. In other words, the angle α formed by an extension line of the upper surface of the piezoelectric body 21 and a tangent line at an arbitrary point of the first end surface 41a is larger than the angle β formed by an extension line of the upper surface of the piezoelectric body 21 and a tangent line at an arbitrary point of the second end surface 41b.

[0050] In elastic wave device 1 in accordance with the second embodiment, the upper surface side of piezoelectric body 21 through which the elastic wave causing main resonance propagates is steep, and first end surface 41a reflects more of the elastic wave to be utilized, contributing to reducing loss.

[0051] In addition, since the end face 41 has the first end face 41a and the second end face 41b with different inclination angles, by adjusting the inclination angles of each, it becomes easy to adjust specific characteristics of the end face 41. For example, it becomes easy to balance loss and spurious.

[0052] [Manufacturing method] A method for manufacturing an acoustic wave device 1 according to the present disclosure will now be described.

[0053] Acoustic wave device 1 is manufactured by laminating substrate 2 and electrode layer 3 in that order. Then, a plurality of strip electrodes 31 are formed above substrate 2.

[0054] 7A, in acoustic wave device 1, mask 5 is formed above strip electrode 31, and etching is performed. End surface 41 can be formed in piezoelectric body 21 by etching.

[0055] 7A, in the acoustic wave device 1, a mask 5 is formed above the strip electrode 31, and etching is performed. By etching, the strip electrode 31 is thinned, and a first strip electrode 315 can be formed.

[0056] The end surface 41 and the first strip electrode 315 may be formed separately by multiple etching steps, or may be formed simultaneously or successively by a single etching step.

[0057] When both the end surface 41 and the first strip electrode 315 are formed by etching, the mask 5 is gradually retracted from the positive direction to the negative direction of the D1 axis by etching as shown in FIG. 7B during the formation of the end surface 41 by appropriately adjusting the material and thickness of the mask 5, the conditions for plasma generation in the dry etching, or various other conditions, so that the end surface 41 side of the first strip electrode 315 is exposed. Since the end surface 41 side is naturally exposed, the mask 5 can be formed so that only the first strip electrode 315 has a smaller average thickness. For example, the mask 5 can be formed so that the second portion 315b is located further in the acoustic wave propagation direction than the first portion 315a.

[0058] Compared to the case where end surface 41 and first strip electrode 315 are etched separately, this avoids the difficulty of accurately forming mask 5, and facilitates the manufacture of acoustic wave device 1. First strip electrode 315 is formed by the recessed mask 5, as shown in Fig. 7C. Finally, mask 5 is removed as shown in Fig. 7D, thereby completing the manufacture of acoustic wave device 1.

[0059] When etching both the end face 41 and the first strip electrode 315, after removing a part of the mask 5 located above the first strip electrode 315, etching may be performed. A part of the first strip electrode 315 is likely to be exposed.

[0060] Also, after a part of the first strip electrode 315 is exposed, as shown in FIG. 7B, the first strip electrode 315 serves as a metal mask. Since the metal mask is less likely to be etched compared to the resin mask, the end face 41 can be formed steeply. In other words, the first end face 41a formed after a part of the first strip electrode 315 is exposed is steeper than the second end face 41b formed before the exposure. The elastic wave device 1 according to the third embodiment can be manufactured. For example, when using an electrode layer 3 containing Ti as a main component, the etching selectivity between LT and Ti is higher than the etching selectivity between LT and Al, so it is likely to function as a metal mask. As a result, the first end face 41a can be made steeper.

[0061] The etching may be performed by dry etching.

[0062] As the mask 5, for example, a resist for i-line may be used. A positive resist type resist may be used. A novolak resin may be used.

[0063] 〔First Usage Example: Demultiplexer〕 FIG. 8 is a circuit diagram schematically showing the configuration of a demultiplexer 8 as a usage example of the elastic wave device 1.

[0064] The demultiplexer 8 has, for example, a transmission filter 83 that filters a transmission signal from a transmission terminal 81 and outputs it to an antenna terminal 82, and a reception filter 85 that filters a reception signal from the antenna terminal 82 and outputs it to a pair of reception terminals 84.

[0065] The transmit filter 83 is configured, for example, by a ladder filter including multiple elastic wave devices 1. That is, the transmit filter 83 has multiple (or one) elastic wave devices 1 connected in series between the transmit terminal 81 and the antenna terminal 82, and multiple (or one) elastic wave devices 1 (parallel arms) connecting the series line (series arm) to a reference potential.

[0066] The receiving filter 85 includes, for example, the acoustic wave device 1 and a multimode filter (including a double-mode filter) 87. The multimode filter 87 has a plurality of IDT electrodes 35 (three in the illustrated example) arranged in the arrangement direction of the plurality of strip electrodes 31.

[0067] Although the description has been given of a case in which the splitter 8 includes the transmission filter 83 and the reception filter 85, the present invention is not limited to this. The splitter 8 may be, for example, a diplexer or a multiplexer including three or more filters.

[0068] [Second usage example: Communication device] 9 is a block diagram showing a main part of a communication device 9 as an example of using the duplexer 8. The communication device 9 performs wireless communication using radio waves, and includes the duplexer 8.

[0069] In the communication device 9, a transmission information signal TIS including information to be transmitted is modulated and frequency-raised (converted to a high-frequency signal of a carrier frequency) by an RF-IC (Radio Frequency Integrated Circuit) 91 to become a transmission signal TS. Unnecessary components outside the transmission passband are removed from the transmission signal TS by a bandpass filter 92a, amplified by an amplifier 93a, and input to a splitter 8 (transmission terminal 81). The splitter 8 (transmission filter 83) then removes unnecessary components outside the transmission passband from the input transmission signal TS, and outputs the transmission signal TS after removal to an antenna terminal 82 or an antenna 95. The antenna 95 converts the input electrical signal (transmission signal TS) into a wireless signal (radio wave) and transmits it.

[0070] In addition, in the communication device 9, a radio signal (radio wave) received by an antenna 95 is converted by the antenna 95 into an electric signal (received signal RS) and input to the duplexer 8 (antenna terminal 82). The duplexer 8 (receiving filter 85) removes unnecessary components outside the receiving passband from the inputted received signal RS, and the signal is amplified by an amplifier 93b from the receiving terminal 84, and the unnecessary components outside the receiving passband are removed by a bandpass filter 92b. The received signal RS is then frequency-downshifted and demodulated by the RF-IC 91 to become a received information signal RIS.

[0071] The transmission information signal TIS and the reception information signal RIS may be low-frequency signals (baseband signals) containing appropriate information, such as analog audio signals or digitized audio signals. The passband of wireless signals (e.g., 5 GHz or higher) may also be used. The modulation method may be any of phase modulation, amplitude modulation, frequency modulation, or a combination of two or more of these. Although the direct conversion method is exemplified in FIG. 9 as the circuit method, other appropriate methods may also be used, such as a double superheterodyne method. Also, FIG. 9 shows only the essential parts in a schematic manner, and a low-pass filter or an isolator, etc. may be added at appropriate positions, and the positions of the amplifiers, etc. may also be changed.

[0072] (summary) (1) An elastic wave device according to a first aspect of the present disclosure includes a substrate having an end surface and a piezoelectric body, and a plurality of strip electrodes located above the substrate and extending in parallel. At least some of the plurality of strip electrodes are excitation sections capable of exciting elastic waves. The end surface is parallel to the direction in which the strip electrodes extend in a plan view from above, and is located in the elastic wave propagation direction relative to the excitation section. The plurality of strip electrodes include a first strip electrode located closest to the end surface in the elastic wave propagation direction, and a second strip electrode farther from the end surface than the first strip electrode in the elastic wave propagation direction. The second strip electrode is an excitation section. In a cross section cut in the elastic wave propagation direction, the average thickness of the first strip electrode is smaller than the average thickness of the second strip electrode.

[0073] (2) In an elastic wave device according to a second aspect of the present disclosure, in the first aspect, the first strip electrode includes a first portion and a second portion having a smaller thickness than the first portion in a cross section cut in the elastic wave propagation direction, and the second portion is located closer to the end face than the first portion in the elastic wave propagation direction.

[0074] (3) An elastic wave device according to a third aspect of the present disclosure is, in the first or second aspect above, a first strip electrode has a lower surface, a first upper surface, a second upper surface located closer to the end surface than the first upper surface in the direction of elastic wave propagation, and a riser surface connecting the first upper surface and the second upper surface, and the first upper surface is located higher than the second upper surface.

[0075] (4) An elastic wave device according to a fourth aspect of the present disclosure is any of the first to third aspects, wherein the first strip electrode has a lower surface, a first surface located on an end surface side of a side surface that is in contact with the lower surface in the elastic wave propagation direction, and an upper surface that is in contact with the first surface. The upper surface is inclined downward with respect to the lower surface.

[0076] (5) An elastic wave device according to a fifth aspect of the present disclosure is any of the first to fourth aspects, wherein the first strip electrode has a lower surface, a first surface located on an end surface side of a side surface that is in contact with the lower surface in the elastic wave propagation direction, an upper surface that is in contact with the first surface, and a second surface that connects the first surface and the upper surface, and the second surface is curved.

[0077] (6) An elastic wave device according to a sixth aspect of the present disclosure is any of the first to fifth aspects, wherein the average thickness of the majority of the strip electrodes forming the excitation portion is the same as that of the second strip electrode.

[0078] (7) An elastic wave device according to a seventh aspect of the present disclosure is, in the first to sixth aspects described above, such that, in a cross section cut in the elastic wave propagation direction, the angle α between an extension of the top surface of the piezoelectric body and a tangent at any point on the end surface is smaller than 90°.

[0079] (8) An elastic wave device according to an eighth aspect of the present disclosure has any of the first to seventh aspects, wherein the angle α is smaller than 82°.

[0080] (9) An elastic wave device according to a ninth aspect of the present disclosure is any of the first to eighth aspects, wherein the end face has a first end face located on an upper surface side of the piezoelectric body and a second end face located on a lower surface side of the piezoelectric body, and in a cross section cut in the elastic wave propagation direction, an angle formed by an extension of the upper surface of the piezoelectric body and a tangent at an arbitrary point to the first end face is larger than an angle formed by an extension of the upper surface of the piezoelectric body and a tangent at an arbitrary point to the second end face.

[0081] (10) The elastic wave device according to a tenth aspect of the present disclosure is any one of the first to ninth aspects, in which the first strip electrode is an excitation portion.

[0082] (11) An elastic wave device according to an eleventh aspect of the present disclosure is any of the first to tenth aspects, in which the first strip electrode is a floating electrode that is not electrically connected to the excitation portion.

[0083] (12) An elastic wave device according to a twelfth aspect of the present disclosure is any of the first to eleventh aspects, wherein the first strip electrode has a larger width in the elastic wave propagation direction than the second strip electrode.

[0084] (13) An acoustic wave device according to a thirteenth aspect of the present disclosure is any one of the first to twelfth aspects, wherein the first strip electrode contains Al as a main component.

[0085] (14) An acoustic wave device according to a fourteenth aspect of the present disclosure is any one of the first to thirteenth aspects, wherein the substrate has a groove on the upper surface, and the end surface is a side surface of the groove.

[0086] (15) According to a fifteenth aspect of the present disclosure, in the elastic wave device according to any one of the first to fourteenth aspects, the substrate includes a support substrate and a first layer located between the support substrate and the piezoelectric body.

[0087] (16) According to a sixteenth aspect of the present disclosure, a method for manufacturing an elastic wave device according to any one of the first to fifteenth aspects includes a first step of forming a plurality of strip electrodes above a substrate, a second step of forming a mask above the strip electrodes after the first step, and a third step of forming an end face on the substrate by etching and removing, by etching, a portion of a first strip electrode that is located closest to the end face in the elastic wave propagation direction among the plurality of strip electrodes.

[0088] (17) A seventeenth aspect of the present disclosure relates to a method for manufacturing an acoustic wave device according to the sixteenth aspect, in which a second step is performed after removing a portion of the mask located above the first strip electrode.

[0089] (18) An eighteenth aspect of the present disclosure provides a method for manufacturing an acoustic wave device according to the seventeenth aspect, wherein in the third step, the mask is gradually retracted in a direction opposite to the acoustic wave propagation direction.

[0090] (19) The demultiplexer according to the 19th aspect of the present disclosure includes an antenna terminal, a transmission filter configured to filter a transmission signal and output it to the antenna terminal, and a reception filter configured to filter a reception signal from the antenna terminal. At least one of the transmission filter and the reception filter includes the surface acoustic wave device of the 1st to 15th aspects.

[0091] (20) The communication device according to the 20th aspect of the present disclosure includes an antenna, the demultiplexer of the 19th aspect having an antenna terminal connected to the antenna, and an IC connected to the transmission filter and the reception filter.

Explanation of Signs

[0092] 1: Surface acoustic wave device 2: Substrate 21: Piezoelectric body 22: First layer 23: Support substrate 3: Electrode layer 31: Strip electrode 311: Excitation part 311a: First excitation part 311b: Second excitation part 3117: Second strip electrode 313: Floating electrode 315: First strip electrode 35: IDT electrode 351: Bus bar 351a: First bus bar 351b: Second bus bar 37: Reflector 4: Groove part 41: End face 41a: First end face 41b: Second end face 5: Mask 8: Demultiplexer 9: Communication device

Claims

1. A substrate having an end surface and a piezoelectric body; a plurality of strip electrodes disposed above the substrate and each strip electrode extends in parallel; having At least a part of the strip electrodes among the plurality of strip electrodes is an excitation portion capable of exciting an acoustic wave, The end surface has a plan view from above, Parallel to the direction in which the strip electrodes extend, Located in the elastic wave propagation direction with respect to the excitation unit, The plurality of strip electrodes include a first strip electrode located closest to the end face in the acoustic wave propagation direction; a second strip electrode that is farther from the end face than the first strip electrode in the elastic wave propagation direction and is the excitation portion; Including, In a cross section cut in the acoustic wave propagation direction, an average thickness of the first strip electrode is smaller than an average thickness of the second strip electrode, the substrate has a groove on an upper surface thereof; The end surface is a part of the side surface of the groove. Elastic wave device.

2. The first strip electrode is A first portion; and A second portion having a smaller thickness than the first portion in the cross section; Including, In the elastic wave propagation direction, the second portion is located closer to the end face than the first portion. The acoustic wave device according to claim 1 .

3. The first strip electrode is The underside and A first top surface; a second upper surface located closer to the end surface than the first upper surface in the elastic wave propagation direction; a riser surface connecting the first upper surface and the second upper surface; having The first upper surface is located above the second upper surface. The acoustic wave device according to claim 1 .

4. The first strip electrode is The underside and a first surface located on the end surface side among side surfaces that contact the lower surface in the elastic wave propagation direction; an upper surface in contact with the first surface; having The upper surface is inclined downward with respect to the lower surface. The acoustic wave device according to claim 1 .

5. The first strip electrode is The underside and a first surface located on the end surface side among side surfaces that contact the lower surface in the elastic wave propagation direction; an upper surface in contact with the first surface; a second surface connecting the first surface and the top surface; having The second surface is curved. The acoustic wave device according to claim 1 .

6. The average thickness of the majority of the strip electrodes that are the excitation portion is the same as that of the second strip electrode. The acoustic wave device according to claim 1 .

7. In the cross section, an angle α between an extension of the top surface of the piezoelectric body and a tangent at any point on the end surface is smaller than 90°. The acoustic wave device according to claim 1 .

8. The angle α is smaller than 82° The acoustic wave device according to claim 7 .

9. The end surface is A first end surface located on an upper surface side of the piezoelectric body; A second end surface located on a lower surface side of the piezoelectric body; having In the cross section, an angle formed by an extension of the upper surface of the piezoelectric body and a tangent at an arbitrary point of the first end face is larger than an angle formed by an extension of the upper surface of the piezoelectric body and a tangent at an arbitrary point of the second end face. The acoustic wave device according to claim 7 .

10. The first strip electrode is the excitation portion. The acoustic wave device according to claim 1 .

11. The first strip electrode is a floating electrode that is not electrically connected to the excitation section. The acoustic wave device according to claim 1 .

12. The first strip electrode has a width in the acoustic wave propagation direction that is larger than that of the second strip electrode. The acoustic wave device according to claim 1 .

13. The first strip electrode contains Al as a main component. The acoustic wave device according to claim 1 .

14. The substrate is A support substrate; a first layer located between the support substrate and the piezoelectric body; have The acoustic wave device according to claim 1 .

15. An antenna terminal; a transmission filter configured to filter a transmission signal and output the filtered signal to the antenna terminal; a receive filter configured to filter a receive signal from the antenna terminal; having A duplexer, wherein at least one of the transmission filter and the reception filter includes the acoustic wave device according to claim 1 .

16. The antenna, The duplexer according to claim 15, wherein the antenna terminal is connected to the antenna; an IC connected to the transmit filter and the receive filter; A communication device having the above configuration.

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