Elastic wave device and communication device

Abstract

The present invention improves the frequency characteristics of an elastic wave device. A first electrode finger includes a first region facing a tip portion of a second electrode finger in a first direction, and a second region positioned closer to the tip side of the first electrode finger than the first region. The first region includes a first area portion in which the cross-sectional area when cut along the first direction in a plan view is a first area. The second region includes a second area portion in which the cross-sectional area when cut along the first direction in a plan view is a second area. The first area is smaller than the second area.

Description

Acoustic wave devices and communication devices

[0001] The present disclosure relates to an acoustic wave device and a communication device.

[0002] Patent Document 1 discloses an acoustic wave device in which first electrode fingers have widened portions.

[0003] International Publication No. 2020 / 100949

[0004] An elastic wave device according to one aspect of the present disclosure includes a piezoelectric body having a groove and an IDT electrode having first and second electrode fingers adjacent to each other, the IDT electrode including a portion located inside the groove, wherein the thickness of the piezoelectric body is less than twice the pitch of the first and second electrode fingers, wherein the arrangement direction of the first and second electrode fingers is defined as a first direction and the longitudinal direction of the first electrode fingers is defined as a second direction, the first electrode fingers include a first region facing a tip of the second electrode finger in the first direction, and a second region located closer to the tip of the first electrode finger than the first region, the first region including a first area portion having a cross-sectional area of ​​a first area when cut along the first direction in a planar view, the second region including a second area portion having a cross-sectional area of ​​a second area when cut along the first direction in a planar view, and the first area being smaller than the second area.

[0005] 1 is a plan view illustrating a schematic configuration of an elastic wave device according to a first embodiment of the present disclosure. FIG. 2 is a cross-sectional view taken along line A-A of FIG. 1. FIG. 3 is a diagram illustrating a first area and a second area. FIG. 4 is a diagram illustrating a second area and a third area. FIG. 5 is a diagram illustrating a fourth area and a fifth area. FIG. 6 is a table illustrating initial conditions in a simulation model of the elastic wave device. FIG. 7 is a graph illustrating frequency characteristics of an LT model in which the duty of the first electrode finger and the second electrode finger is set to 0.6 in a portion where a first region faces the tip of the second electrode finger. FIG. 8 is a graph illustrating frequency characteristics of an LT model in which the duty of the first electrode finger and the second electrode finger is set to 0.6 in a portion where a first region faces the tip of the second electrode finger. FIG. 9 is a graph illustrating frequency characteristics of an LT model in which the duty of the first electrode finger and the second electrode finger is set to 0.6 in a portion where a first region faces the tip of the second electrode finger. FIG. 10 is a graph illustrating frequency characteristics of an LT model in which the duty of the first electrode finger and the second electrode finger is set to 0.6 in a portion where a first region faces the tip of the second electrode finger. 10 is a graph showing the frequency characteristics of an LT model in which the duty of the first electrode finger and the second electrode finger is set to 0.4 in a portion where the first region faces the tip of the second electrode finger. 11 is a graph showing the frequency characteristics of an LT model in which the duty of the first electrode finger and the second electrode finger is set to 0.4 in a portion where the first region faces the tip of the second electrode finger. 12 is a graph showing the frequency characteristics of an LT model in which the duty of the first electrode finger and the second electrode finger is set to 0.4 in a portion where the first region faces the tip of the second electrode finger. 13 is a graph showing the frequency characteristics of an LT model in which the duty of the first electrode finger and the second electrode finger is set to 0.4 in a portion where the first region faces the tip of the second electrode finger. 14 is a graph showing the frequency characteristics of an LN model in which the duty of the first electrode finger and the second electrode finger is set to 0.4 in a portion where the first region faces the tip of the second electrode finger. 10 is a graph showing the frequency characteristics of an LN model in which the duty of the first electrode finger and the second electrode finger is set to 0.4 in a portion where the first region faces the tip of the second electrode finger, and the duty of the first electrode finger and the second electrode finger is set to 0.4 in a portion where the first region faces the tip of the second electrode finger.10 is a graph showing frequency characteristics of an LN model in which the duty of the first electrode finger and the second electrode finger is set to 0.4 in a portion where the first region faces the tip of the second electrode finger. 11 is a cross-sectional view showing a schematic configuration of an elastic wave device according to a second embodiment of the present disclosure. 12 is a schematic diagram of a communication device according to a third embodiment of the present disclosure.

[0006] It is expected that spurious components can be reduced and the frequency characteristics of an acoustic wave device can be improved. According to one aspect of the present disclosure, the frequency characteristics of an acoustic wave device can be improved.

[0007] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The following describes an embodiment of the present disclosure. For convenience of explanation, the same reference numerals are used to designate components having the same functions as those previously described, and the description thereof may not be repeated.

[0008] 1 is a plan view illustrating a schematic configuration of an elastic wave device 101 according to a first embodiment of the present disclosure. FIG. 2 is a cross-sectional view taken along line AA in FIG.

[0009] The acoustic wave device 101 includes a piezoelectric body 1, an IDT electrode 2, multiple multilayer reflective films 3, and a support substrate 4. The support substrate 4, multiple multilayer reflective films 3, piezoelectric body 1, and IDT electrode 2 are stacked in this order. Each of the multiple multilayer reflective films 3 includes, in order from the piezoelectric body 1 side, a low acoustic impedance layer 5 and a high acoustic impedance layer 6. As an example, the acoustic wave device 101 includes four multilayer reflective films 3. IDT is an abbreviation for interdigital transducer.

[0010] Grooves 7 are formed on the surface of the piezoelectric body 1. The piezoelectric body 1 is made of LiTaO ３ and LiNbO ３ The alloy may contain at least one of: ３ LiNbO can also be called lithium tantalate and can be abbreviated as LT. ３ It can also be called lithium niobate and can be expressed as LN. The thickness of the piezoelectric body 1 is T1.

[0011] The IDT electrode 2 is located in a layer above the piezoelectric body 1. The IDT electrode 2 includes a portion located inside the groove 7. In FIG. 1 , the entire portion of the IDT electrode 2 shown in FIG. 1 is located inside the groove 7. The entire IDT electrode 2 may be located inside the groove 7, or only a portion of the IDT electrode 2 may be located inside the groove 7.

[0012] The multilayer reflective film 3, i.e., the low acoustic impedance layer 5 and the high acoustic impedance layer 6, are located below the piezoelectric body 1. The acoustic impedance of the low acoustic impedance layer 5 is lower than the acoustic impedance of the high acoustic impedance layer 6. The low acoustic impedance layer 5 is made of SiO ２ The high acoustic impedance layer 6 may contain HfO ２ , Ta ２ O ５ , and ZrO ２ The acoustic wave device 101 may be interpreted as an acoustic reflection film structure including the multilayer reflection film 3.

[0013] The support substrate 4 supports the piezoelectric body 1, the IDT electrode 2, and the plurality of multilayer reflective films 3. The support substrate 4 may be a Si substrate.

[0014] The IDT electrode 2 has first electrode fingers 8, second electrode fingers 9, bus bars 10, and bus bars 11. The first electrode fingers 8 and the second electrode fingers 9 are adjacent to each other. The bus bars 10 are electrically connected to the first electrode fingers 8. The bus bars 11 are electrically connected to the second electrode fingers 9.

[0015] 1 and 2 show a first direction D1, a second direction D2, and a third direction D3. The first direction D1 can be defined as the arrangement direction of the first electrode fingers 8 and the second electrode fingers 9. The second direction D2 can be defined as the longitudinal direction of the first electrode fingers 8 and the longitudinal direction of the second electrode fingers 9. The third direction D3 can be defined as the thickness direction of the piezoelectric body 1. The first direction D1, the second direction D2, and the third direction D3 may be perpendicular to one another.

[0016] Pitch p of first electrode fingers 8 and second electrode fingers 9 can be defined as the distance between center 12 of first electrode finger 8 and center 13 of second electrode finger 9 in first direction D1. Pitch refers to the center-to-center distance, and can also be said to refer to the repetition interval. Thickness T1 of piezoelectric body 1 is equal to or less than twice pitch p of first electrode fingers 8 and second electrode fingers 9. This allows for the configuration of elastic wave device 101 that is suited to the wavelength of elastic waves propagating within piezoelectric body 1.

[0017] The first electrode finger 8 includes a first region 14 and a second region 15. The first region 14 is a region facing a tip 16 of the second electrode finger 9 in the first direction D1. The second region 15 is a region located closer to the tip 17 of the first electrode finger 8 than the first region 14.

[0018] In the description of the embodiments of the present disclosure, "edge" means a point at the edge of an object, and "end" means a region at the edge of an object. In other words, "end" can be interpreted as a region that includes the "edge."

[0019] The first region 14 includes a first area portion 18 having a cross-sectional area of ​​a first area R1 when the first area portion 18 is cut along the first direction D1 in a plan view. Specifically, the plan view refers to a plan view of the elastic wave device 101, which is the same as the viewpoint in FIG. 1 . The cross section B-B in FIG. 1 is an example of a cross section of the first area portion 18 cut along the first direction D1 in a plan view.

[0020] The second region 15 includes a second area portion 19 having a cross-sectional area of ​​a second area R2 when the second area portion 19 is cut along the first direction D1 in a plan view. The CC cross section in Figure 1 is an example of a cross section of the second area portion 19 when cut along the first direction D1 in a plan view.

[0021] 3 is a diagram illustrating the first area R1 and the second area R2. In FIG. 3, the first area 18 is shown in the form of a cross-sectional view taken along line B-B in FIG. 1, and the second area 19 is shown in the form of a cross-sectional view taken along line C-C in FIG. 1. The first area R1 is smaller than the second area R2.

[0022] According to the acoustic wave device 101, it is possible to realize an acoustic wave device in which spurious components are reduced, that is, in which frequency characteristics are improved.

[0023] The duty of the first electrode finger 8 and the second electrode finger 9 is set to a first value where the first region 14 faces the tip 16 of the second electrode finger 9, and a second value, which is the maximum value, where the second region 15 faces the second electrode finger 9. The duty of the first electrode finger 8 and the second electrode finger 9 can be defined as the ratio of the sum of the width of the first electrode finger 8 and the width of the second electrode finger 9 to twice the pitch p. The difference between the second value and the first value may be 0.05 or more and 0.2 or less. If the difference is less than 0.05, the effect of reducing spurious emissions may be reduced. If the difference is more than 0.2, spurious emissions may occur at frequencies lower than the resonant frequency.

[0024] The length L1 of the opposing portion between the first region 14 and the tip 16 of the second electrode finger 9 in the second direction D2 may be equal to or greater than the pitch p and equal to or less than 2.5 times the pitch p. If the length L1 is less than the pitch p, the effect of reducing spurious emissions may be reduced. If the length L1 exceeds 2.5 times the pitch p, spurious emissions may occur at frequencies lower than the resonant frequency.

[0025] The IDT electrode 2 may include a bus bar 10 electrically connected to the first electrode fingers 8, and dummy electrode fingers 20 extending from the bus bar 10 in the second direction D2 and facing the second electrode fingers 9 in the second direction D2. The dummy electrode fingers 20 may have a function of more precisely controlling the frequency characteristics of the acoustic wave device 101.

[0026] The length L2 in the second direction D2 from the tip 21 of the dummy electrode finger 20 to the region edge 22, which is the end of the first region 14 on the second region 15 side, may be 1.5 times or more and 2.5 times or less than the pitch p. If the length L2 is less than 1.5 times the pitch p, the effect of reducing spurious emissions may be reduced. If the length L2 exceeds 2.5 times the pitch p, spurious emissions may occur at frequencies lower than the resonant frequency.

[0027] The dummy electrode finger 20 includes a third area portion 23, the cross-sectional area of ​​which when the third area portion 23 is cut along the first direction D1 in a plan view is a third area R3. The cross section DD in FIG. 1 is an example of a cross section when the third area portion 23 is cut along the first direction D1 in a plan view.

[0028] 4 is a diagram illustrating the second area R2 and the third area R3. In FIG. 4, the second area 19 is shown in the form of a cross-sectional view taken along line CC in FIG. 1, and the third area 23 is shown in the form of a cross-sectional view taken along line DD in FIG. 1. The third area R3 may be smaller than the second area R2. The third area R3 may be 90% or more and 110% or less of the first area R1.

[0029] The second electrode finger 9 may include a third region 24 and a fourth region 25. The third region 24 is a region facing a tip 26 of the first electrode finger 8 in the first direction D1. The fourth region 25 is a region located closer to the tip 27 of the second electrode finger 9 than the third region 24.

[0030] The third region 24 may include a fourth area portion 28 having a cross-sectional area of ​​a fourth area R4 when the fourth area portion 28 is cut along the first direction D1 in a plan view. The E-E cross section in FIG. 1 is an example of a cross section when the fourth area portion 28 is cut along the first direction D1 in a plan view.

[0031] The fourth region 25 may include a fifth area portion 29 having a cross-sectional area of ​​a fifth area R5 when the fifth area portion 29 is cut along the first direction D1 in a plan view. The cross section F-F in FIG. 1 is an example of a cross section when the fifth area portion 29 is cut along the first direction D1 in a plan view.

[0032] 5 is a diagram illustrating the fourth area R4 and the fifth area R5. In FIG. 5, the fourth area 28 is shown in the form of a cross-sectional view taken along line E-E in FIG. 1, and the fifth area 29 is shown in the form of a cross-sectional view taken along line F-F in FIG. 1. The fourth area R4 may be smaller than the fifth area R5.

[0033] The duty of the first electrode finger 8 and the second electrode finger 9 is set to a first value in the portion where the first region 14 faces the tip 16 of the second electrode finger 9, and to a fourth value in the portion where the second region 15 faces the fourth region 25. The difference between the fourth value and the first value may be 0.05 or more and 0.2 or less. If the difference is less than 0.05, the effect of reducing spurious emissions may be reduced. If the difference is more than 0.2, spurious emissions may occur at frequencies lower than the resonant frequency.

[0034] The acoustic wave device 101 is an antisymmetric mode A １ The vibration mode of the elastic wave device 101 that excites bulk waves may be a thickness shear mode. The elastic wave device 101 that excites bulk waves may not include the multilayer reflective film 3.

[0035] When the material of the piezoelectric body 1 is LT, the cut angle of the piezoelectric body 1 may be, for example, (0°±10°, 0° or more and 55° or less, 0°±10°) in Euler angle (φ, θ, ψ) notation.

[0036] When the material of the piezoelectric body 1 is LN, the cut angle of the piezoelectric body 1 may be, for example, (0°±10°, -15° to 67°, ψ) in Euler angle notation. It may also be (0°±5°, -15° to 67°, ψ), where ψ is 0° to 360°. From another perspective, a Z-cut substrate may be used.

[0037] 1 and 2 are schematic diagrams of a cut-out portion of the acoustic wave device. In reality, a large number of first electrode fingers 8 and second electrode fingers 9 may be periodically arranged in the first direction D1.

[0038] A simulation was performed to verify the effect of the acoustic wave device 101. １ This is a simulation example for exploring conditions under which a SAW resonator in a certain mode can be efficiently excited. The effects of the present disclosure are not limited to these conditions, and each condition can be appropriately optimized to achieve characteristics tailored to the purpose. SAW stands for Surface Acoustic Wave.

[0039] 6 is a table showing the initial conditions for the simulation model of elastic wave device 101. For convenience, the simulation model of elastic wave device 101 will be referred to simply as elastic wave device 101 in the descriptions of FIGS. 6 to 18. Unless otherwise specified, the configuration of elastic wave device 101 is as per the initial conditions.

[0040] Duty: Duty of the first electrode finger 8 and the second electrode finger 9 in the opposing portion of the second region 15 and the fourth region 25. Corresponding to the second and fourth values. Overlap width: Length in the second direction D2 of the portion where the first electrode finger 8 and the second electrode finger 9 oppose each other in the first direction D1. The material of the IDT electrode 2 is Al. The material of the low acoustic impedance layer 5 is SiO. ２ The material of the high acoustic impedance layer 6 is HfO ２ The definitions in FIG. 6 are as described above.

[0041] 6 to 18, for convenience, an elastic wave device 101 in which the piezoelectric body 1 is made of LT will be referred to as an LT model, and an elastic wave device 101 in which the piezoelectric body 1 is made of LN will be referred to as an LN model.

[0042] 7 to 10 are graphs showing the frequency characteristics of the LT model in which the duty of the first electrode fingers 8 and the second electrode fingers 9 is set to 0.6 in the opposing portion between the first region 14 and the tip portion 16. As can be seen from Figs. 7 to 10, the transverse mode spurious is large in the LT model, and the frequency characteristics are not good.

[0043] Duty 0.5: Characteristics when the duty of the first electrode finger 8 and the second electrode finger 9 in the opposing portion between the first region 14 and the tip portion 16 is 0.5, i.e., the initial condition. Duty 0.6: Characteristics when the duty of the first electrode finger 8 and the second electrode finger 9 in the opposing portion between the first region 14 and the tip portion 16 is 0.6. The definitions in Figures 7 to 10 are as described above.

[0044] The phase of the impedance is related to the loss of the acoustic wave device. At frequencies lower than the resonant frequency and higher than the anti-resonant frequency, the closer the phase is to -90°, the smaller the loss. Furthermore, between the resonant frequency and the anti-resonant frequency, the closer the phase is to +90°, the smaller the loss.

[0045] 11 to 14 are graphs showing the frequency characteristics of the LT model in which the duty of the first electrode fingers 8 and the second electrode fingers 9 is set to 0.4 in the opposing portion between the first region 14 and the tip portion 16. As can be seen from Figs. 11 to 14, the LT model has small transverse mode spurious emissions and good frequency characteristics.

[0046] Duty 0.5: Characteristics when the duty of the first electrode finger 8 and the second electrode finger 9 in the opposing portion between the first region 14 and the tip portion 16 is 0.5, i.e., the initial condition.Duty 0.4: Characteristics when the duty of the first electrode finger 8 and the second electrode finger 9 in the opposing portion between the first region 14 and the tip portion 16 is 0.4.The definitions in Figures 11 to 14 and Figures 15 to 18 described below are as described above.

[0047] 15 to 18 are graphs showing the frequency characteristics of the LN model in which the duty of the first electrode fingers 8 and the second electrode fingers 9 is set to 0.4 in the opposing portion between the first region 14 and the tip portion 16. As can be seen from Fig. 15 to 18, the LN model has small transverse mode spurious and good frequency characteristics.

[0048] According to Figures 11 to 18, in at least a portion between the first region 14 and the connection portion between the first electrode finger 8 and the bus bar 10, the cross-sectional area when cut along the first direction D1 in a planar view may be smaller than the second area R2.

[0049] 11 to 18, the difference between the second value and the first value and the difference between the fourth value and the first value are 0.1, but the effects of elastic wave device 101 are expected if the difference is within a range of 0.5 to 2 times this 0.1. In other words, the effects of elastic wave device 101 are expected if the difference in duty is within a range of 0.05 to 0.2.

[0050] 19 is a cross-sectional view showing a schematic configuration of an elastic wave device 101 according to a second embodiment of the present disclosure. As shown in Fig. 19, elastic wave device 101 may have a membrane structure. Elastic wave device 101 with a membrane structure shown in Fig. 19 does not need to include multilayer reflective film 3. Instead, an opening 30 is formed in support substrate 4 on the side of piezoelectric body 1, and piezoelectric body 1 is provided to cover opening 30.

[0051] 20 is a schematic diagram of a communication device 201 according to a third embodiment of the present disclosure. The communication device 201 is an application example of the acoustic wave device 101 and performs wireless communication using radio waves. The communication device 201 may include a transmit filter 111 and a receive filter 112. Each of the transmit filter 111 and the receive filter 112 may include the acoustic wave device 101.

[0052] In the communication device 201, a transmission information signal TIS containing information to be transmitted may be modulated and frequency-raised by an RF-IC 113 and converted into a transmission signal TS. RF-IC is an abbreviation for Radio Frequency-Integrated Circuit. Raising the frequency is, in other words, conversion to a high-frequency signal having a carrier frequency. A band-pass filter 114 may remove unnecessary components from the transmission signal TS outside the transmission passband. The transmission signal TS after removing the unnecessary components may then be amplified by an amplifier 115 and input to the transmission filter 111.

[0053] The transmission filter 111 may remove unnecessary components outside the transmission passband from the input transmission signal TS. The transmission filter 111 may output the transmission signal TS after removing the unnecessary components to the antenna 116 via an antenna terminal. The antenna 116 may convert the transmission signal TS, which is an electrical signal input thereto, into radio waves as a wireless signal and transmit the radio waves to the outside of the communication device 201.

[0054] Furthermore, the antenna 116 may convert the received external radio waves into a received signal RS, which is an electrical signal, and input the received signal RS to the receive filter 112 via the antenna terminal. The receive filter 112 may remove unnecessary components outside the receive passband from the input received signal RS. The receive filter 112 may output the received signal RS after the unnecessary components have been removed to the amplifier 117. The output received signal RS may be amplified by the amplifier 117. The bandpass filter 118 may remove unnecessary components outside the receive passband from the amplified received signal RS. The received signal RS after the unnecessary components have been removed may be frequency-downgraded and demodulated by the RF-IC 113, and converted into a received information signal RIS.

[0055] The transmit information signal TIS and the receive information signal RIS may be low-frequency signals containing appropriate information. The low-frequency signals may be baseband signals. For example, the transmit information signal TIS and the receive information signal RIS may be analog audio signals or digitized audio signals. The passband of the radio signals may be set appropriately and may comply with various known standards.

[0056] [Summary] An elastic wave device according to a first aspect of the present disclosure includes a piezoelectric body having a groove and an IDT electrode having first and second electrode fingers adjacent to each other, the IDT electrode including a portion located inside the groove, wherein the thickness of the piezoelectric body is equal to or less than twice the pitch of the first and second electrode fingers, wherein a first direction is an arrangement direction of the first and second electrode fingers and a second direction is a longitudinal direction of the first electrode fingers, the first electrode fingers include a first region facing a tip of the second electrode finger in the first direction and a second region located closer to the tip of the first electrode finger than the first region, the first region includes a first area portion having a cross-sectional area of ​​a first area when cut along the first direction in a plan view, the second region includes a second area portion having a cross-sectional area of ​​a second area when cut along the first direction in a plan view, and the first area is smaller than the second area.

[0057] An elastic wave device according to aspect 2 of the present disclosure is the same as aspect 1, in that the duty of the first electrode finger and the second electrode finger is a first value at the opposing portion between the first region and the tip of the second electrode finger, and the maximum value is a second value at the opposing portion between the second region and the second electrode finger, and the difference between the second value and the first value is 0.05 or more and 0.2 or less.

[0058] An elastic wave device according to aspect 3 of the present disclosure is, in aspect 1 or 2, such that the length of the opposing portion between the first region and the tip of the second electrode finger in the second direction is equal to or greater than the pitch and equal to or less than 2.5 times the pitch.

[0059] An elastic wave device according to aspect 4 of the present disclosure is any one of aspects 1 to 3, wherein the IDT electrode includes a bus bar electrically connected to the first electrode finger and a dummy electrode finger extending from the bus bar in the second direction and facing the second electrode finger in the second direction.

[0060] An elastic wave device according to aspect 5 of the present disclosure is the same as aspect 4, wherein the length in the second direction from the tip of the dummy electrode finger to the end of the first region on the second region side is 1.5 times or more and 2.5 times or less than the pitch.

[0061] An elastic wave device according to aspect 6 of the present disclosure is, in aspect 4 or 5, such that the dummy electrode finger includes a third area portion whose cross-sectional area when cut along the first direction in the planar view is a third area, and the third area is smaller than the second area.

[0062] An elastic wave device according to aspect 7 of the present disclosure is any one of aspects 4 to 6, wherein the dummy electrode finger includes a third area portion whose cross-sectional area when cut along the first direction in the planar view is a third area, and the third area is 90% or more and 110% or less of the first area.

[0063] An elastic wave device according to aspect 8 of the present disclosure is an elastic wave device according to any one of aspects 1 to 7, wherein the second electrode finger includes a third region facing the tip of the first electrode finger in the first direction and a fourth region located closer to the tip of the second electrode finger than the third region, the third region including a fourth area portion having a cross-sectional area of ​​a fourth area when cut along the first direction in the planar view, the fourth region including a fifth area portion having a cross-sectional area of ​​a fifth area when cut along the first direction in the planar view, and the fourth area being smaller than the fifth area.

[0064] An elastic wave device according to aspect 9 of the present disclosure is the same as aspect 8, wherein the duty of the first electrode finger and the second electrode finger is a first value at the opposing portion between the first region and the tip of the second electrode finger, and a fourth value at the opposing portion between the second region and the fourth region, and the difference between the fourth value and the first value is 0.05 or more and 0.2 or less.

[0065] The elastic wave device according to a tenth aspect of the present disclosure is the elastic wave device according to any one of the first to ninth aspects, further comprising: １ Exciting the mode.

[0066] An elastic wave device according to an eleventh aspect of the present disclosure is the elastic wave device of any one of the first to ninth aspects, in which bulk waves are excited.

[0067] An elastic wave device according to a twelfth aspect of the present disclosure is the elastic wave device of any one of the first to eleventh aspects, which has an acoustic reflection film structure or a membrane structure.

[0068] A communication device according to a thirteenth aspect of the present disclosure includes the acoustic wave device according to any one of the first to twelfth aspects.

[0069] The present disclosure is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present disclosure.

[0070] REFERENCE SIGNS LIST 1 Piezoelectric body 2 IDT electrode 3 Multilayer reflective film 4 Support substrate 5 Low acoustic impedance layer 6 High acoustic impedance layer 7 Groove 8 First electrode finger 9 Second electrode finger 10, 11 Bus bar 12 Center of first electrode finger in first direction 13 Center of second electrode finger in first direction 14 First region 15 Second region 16 Tip of second electrode finger 17 Tip of first electrode finger 18 First area 19 Second area 20 Dummy electrode finger 21 Tip of dummy electrode finger 22 Region edge 23 Third area 24 Third region 25 Fourth region 26 Tip of first electrode finger 27 Tip of second electrode finger 28 Fourth area 29 Fifth area 30 Opening 101 Acoustic wave device 201 Communication device D1 First direction D2 Second direction D3 Third direction L1 L2: Length in the second direction of the opposing portion between the first region and the tip of the second electrode finger. L3: Length in the second direction from the tip of the dummy electrode finger to the end of the first region on the second region side. p: Pitch of the first electrode finger and the second electrode finger. R1: First area. R2: Second area. R3: Third area. R4: Fourth area. R5: Fifth area. T1: Thickness of the piezoelectric body.

Claims

1. An elastic wave device comprising: a piezoelectric body having a groove; and an IDT electrode having first and second electrode fingers adjacent to each other, including a portion located inside the groove; a thickness of the piezoelectric body is less than twice the pitch of the first and second electrode fingers; a first direction is an arrangement direction of the first and second electrode fingers and a second direction is a longitudinal direction of the first electrode fingers, the first electrode fingers include a first region facing a tip of the second electrode finger in the first direction and a second region located closer to the tip of the first electrode finger than the first region, the first region includes a first area portion having a cross-sectional area of ​​a first area when cut along the first direction in a plan view, and the second region includes a second area portion having a cross-sectional area of ​​a second area when cut along the first direction in a plan view, and the first area is smaller than the second area.

2. The elastic wave device of claim 1, wherein the duty of the first electrode finger and the second electrode finger is a first value at the opposing portion between the first region and the tip of the second electrode finger, and a second value is the maximum value at the opposing portion between the second region and the second electrode finger, and the difference between the second value and the first value is 0.05 or more and 0.2 or less.

3. An elastic wave device as described in claim 1 or 2, wherein the length of the opposing portion between the first region and the tip of the second electrode finger in the second direction is greater than or equal to the pitch and less than 2.5 times the pitch.

4. An elastic wave device described in any one of claims 1 to 3, wherein the IDT electrode has: a bus bar electrically connected to the first electrode finger; and a dummy electrode finger extending from the bus bar in the second direction and facing the second electrode finger in the second direction.

5. The elastic wave device as described in claim 4, wherein the length in the second direction from the tip of the dummy electrode finger to the end of the first region on the second region side is not less than 1.5 times the pitch and not more than 2.5 times the pitch.

6. The elastic wave device of claim 4 or 5, wherein the dummy electrode finger includes a third area portion having a cross-sectional area of ​​a third area when cut along the first direction in the planar view, and the third area is smaller than the second area.

7. An elastic wave device as described in any one of claims 4 to 6, wherein the dummy electrode finger includes a third area portion having a cross-sectional area of ​​a third area when cut along the first direction in the planar view, and the third area is 90% or more and 110% or less of the first area.

8. An elastic wave device as claimed in any one of claims 1 to 7, wherein the second electrode finger includes a third region facing the tip of the first electrode finger in the first direction and a fourth region located closer to the tip of the second electrode finger than the third region, the third region includes a fourth area portion having a cross-sectional area of ​​a fourth area when cut along the first direction in the planar view, the fourth region includes a fifth area portion having a cross-sectional area of ​​a fifth area when cut along the first direction in the planar view, and the fourth area is smaller than the fifth area.

9. The elastic wave device of claim 8, wherein the duty of the first electrode finger and the second electrode finger is a first value at a portion where the first region faces the tip of the second electrode finger and a fourth value at a portion where the second region faces the fourth region, and a difference between the fourth value and the first value is 0.05 or more and 0.2 or less.

10. Antisymmetric mode A １ The acoustic wave device according to claim 1 , wherein a mode is excited.

11. The acoustic wave device according to claim 1, which excites bulk waves.

12. The acoustic wave device according to claim 1, which has an acoustic reflection film structure or a membrane structure.

13. A communication device comprising the acoustic wave device according to any one of claims 1 to 12.

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