Elastic wave device

Abstract

The present invention relates to an elastic wave device provided with a coil element located above a circuit pattern including a resonator. The reflector constituting the resonator is constituted by: in the propagation direction x of an elastic surface wave, arranging a plurality of reflector elements constituted by two adjacent electrode fingers and a first bus bar connecting the two electrode fingers at one end side in the propagation direction x; and connecting the other end side of the two electrode fingers of each of the plurality of reflector elements to a second bus bar extending in the propagation direction x, respectively. The coil element has an IDT electrode upper portion located above the formation region of the IDT electrode, and a reflector upper portion located above the formation region of the reflector. While the coil element is arranged above the resonator formation region with an air gap formed therebetween, reduction in the coil Q value is suppressed as much as possible.

Description

Technical Field

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

[0002] Elastic wave devices are used as frequency filters in mobile communication devices and the like. To impart the desired characteristics to such elastic wave devices, it is known that elastic wave devices have coil elements incorporated in their formed filter circuits (see Patent Document 1).

[0003] As in patent document 1 Figure 4 As shown, in the substrate (device chip) constituting the elastic wave device, a space is formed in the region where the resonator is formed.

[0004] On the other hand, as in Patent Document 1 Figure 3 As shown, the coil element is formed on the substrate in a region located to the side of the resonator formation region.

[0005] If the coil element is positioned above the resonator formation area and an air gap is formed between it and the resonator, there is no need to ensure a dedicated area for the coil element on the substrate, which helps to meet the miniaturization requirements of elastic wave devices.

[0006] However, in designs where the coil element is placed close to the resonator forming region, since the reflector constituting the resonator is usually not connected to the outside and forms a closed path (closed loop), it is expected that the Q value of the coil will be significantly reduced due to the eddy current effect from the coil.

[0007] Patent Document 1: International Publication No. 2010 / 125873. Summary of the Invention

[0008] The main problem to be solved by the present invention is to suppress the decrease in the Q value of the coil as much as possible while placing the coil element for imparting the required characteristics to the elastic wave device on the resonator forming region and forming an air gap between it and the resonator.

[0009] To address the aforementioned issues, in this invention, from a first perspective, the elastic wave device is constructed to include: A device chip having at least one functional surface made of piezoelectric material; A circuit pattern consisting of a conductive metal layer and containing multiple resonators, formed on the functional surface; And a coil element made of conductive metal, the coil element being located on a virtual first plane along the surface of the conductive metal layer, and being configured such that its lower surface is along a virtual second plane parallel to the first plane and forming a predetermined gap between the first plane; in, The resonator is constructed by arranging IDT electrodes between the reflectors; At least a portion of the resonators are resonators with a unique structure, which is configured in such a way that, in the propagation direction of the elastic surface wave excited by the IDT electrodes, a plurality of reflector elements are arranged along the propagation direction, each consisting of two adjacent electrode fingers extending in a direction orthogonal to the propagation direction and a first busbar connecting the two electrode fingers at one end; and, in a second busbar extending along the propagation direction, the other ends of the two electrode fingers of each of the plurality of reflector elements are respectively connected. and, The coil element is configured to have: an upper portion of the IDT electrode located above the IDT electrode forming region in the resonator of the unique structure, and an upper portion of the reflector located above the reflector forming region.

[0010] In one embodiment of the invention, the upper portion of the IDT electrode in the coil element is configured to extend along the propagation direction of the elastic surface wave, and the upper portion of the reflector in the coil element is configured to have a parallel portion extending along the propagation direction of the elastic surface wave and an intersecting portion orthogonal to the propagation direction.

[0011] In addition, as one embodiment of the present invention, the device chip has a rectangular outline when viewed from a direction orthogonal to the functional surface, and the coil element is constructed to be square and a single-turn structure when viewed from a direction orthogonal to the functional surface, and has two length side portions arranged along the long side direction of the device chip, and two width side portions arranged along the short side direction of the device chip.

[0012] In addition, as an embodiment of the present invention, the distance between the first plane and the second plane is set to be 0.5 μm or more and 3 μm or less.

[0013] In one embodiment of the present invention, the reflector consists of three reflector elements and a second busbar.

[0014] In one embodiment of the present invention, the reflector is not connected to the outside, but forms a closed path.

[0015] In one embodiment of the present invention, the reflector as a whole has an even number of electrode fingers.

[0016] In one embodiment of the present invention, in one of the two reflectors constituting the resonator, the second busbar is disposed on one side of the two boundaries along the propagation direction x in the forming region of the resonator, while in the other of the two reflectors constituting the resonator, the second busbar is disposed on the other side of the two boundaries along the propagation direction x in the forming region of the resonator.

[0017] In one embodiment of the present invention, the thickness of the conductive metal layer is 0.15 to 0.5 μm.

[0018] In one embodiment of the present invention, the thickness of the coil element is 2 to 5 μm and its width is 20 to 50 μm.

[0019] In this type of elastic wave device, even with a design that places the coil element close to the resonator forming region, it has been confirmed that by having the reflector configured with at least two of the reflector elements and the second busbar, the reduction in the coil Q value can be suppressed as much as possible. Attached Figure Description

[0020] Figure 1 This is a three-dimensional structural schematic diagram of an elastic wave device related to one embodiment of the present invention, wherein a portion of the resonator formed on the functional surface is represented by solid lines, coil elements are represented by dashed lines, and the remaining structure is omitted.

[0021] Figure 2 This is a schematic diagram of the planar structure of the key part of the elastic wave device.

[0022] Figure 3 yes Figure 2 A schematic diagram of the cross-sectional structure along line A-A.

[0023] Figure 4 yes Figure 2 A schematic diagram of the cross-sectional structure along line B-B.

[0024] Figure 5 yes Figure 2 A schematic diagram of the magnified structure of the upper-middle resonator.

[0025] Figure 6 yes Figure 2 A schematic diagram of the magnified structure of the lower-middle resonator.

[0026] Figures 7(a) and 7(b) are circuit diagrams illustrating an example of a circuit formed on the functional surface of the device chip.

[0027] Figure 8 This is a planar structural schematic diagram showing the key components of the embodiment, wherein the resonator is represented by solid lines and the coil element is represented by dashed lines.

[0028] Figure 9 This is a planar structural schematic diagram showing the key components of the configuration of Comparative Example 1, in which the resonator is represented by solid lines and the coil element by dashed lines.

[0029] Figure 10 This is a planar structural schematic diagram showing the key components of the configuration of Comparative Example 2, in which the resonator is represented by solid lines and the coil element by dashed lines.

[0030] Figures 11(a) and 11(b) show the simulation results for the embodiments, comparative example 1 and comparative example 2.

[0031] Figure label: S1 First Plane S2 Second Plane 1. Elastic wave device 2. Device Chips 2a Functional Surface 2b Back 2c Side View 3. Conductive metal layer 3a surface 4, 4′, 4a, 4b resonators 40 Reflectors 40a electrode finger 40b First busbar 40C Reflector Element 40d Second busbar 40e busbar 41 IDT Electrode 41a Electrode Finger 41b Busbar 5 ports 6. Grounding 7. Coil Components 7a IDT electrode upper part 7b Upper part of the reflector 7c Parallel section 7d Intersection 7e Length side portion 7f Width Side 7g per side 7h The other side 8. Wiring between resonators 9. External connection wiring 10 pillars. Detailed Implementation

[0032] The following will refer to Figures 1 to 11. A typical embodiment of the present invention will be described. The elastic wave device 1 according to this embodiment is suitable for use as a frequency filter in mobile communication devices, etc.

[0033] The elastic wave device 1 according to this embodiment is constructed by forming a circuit pattern of conductive metal layer 3 on the functional surface 2a of a single device chip 2 having at least one side of a functional surface 2a made of piezoelectric material.

[0034] like Figure 1 As shown, typically, device chip 2 has a functional surface 2a formed by the piezoelectric material, and a back surface 2b opposite to the functional surface 2a. Figure 1 As shown, the device chip 2 also has four sides 2c, and the whole is in the shape of a flat hexahedron.

[0035] Lithium tantalate or lithium niobate can typically be used as the piezoelectric element.

[0036] The device chip 2 can also be constructed by stacking materials such as sapphire, silicon, alumina, spinel, quartz or glass on the piezoelectric body.

[0037] On the other hand, the circuit pattern includes a plurality of resonators 4, resonator wiring 8 for connecting each resonator 4 to the outside (see Figure 7), and external connection wiring 9 for connecting the resonators 4 to the outside (see Figure 7).

[0038] In the illustrated example, the circuit pattern contains five resonators. Figure 1 In the circuit shown in Figure 7, the two resonators 4 connected in parallel (i.e., the resonators 4′ with the special structure described later) are represented by solid lines, while the remaining three resonators 4 are represented by imaginary lines to indicate their forming regions.

[0039] By mounting the device chip 2 onto a packaging substrate (not shown) using bumps or the like, a space is formed above the resonator 4, thereby constructing an elastic wave device 1 with a CSP (Chip Size Package) structure.

[0040] In addition, by forming a wall layer (not shown) around the resonator 4 on the functional surface 2a of the device chip 2, and forming a capping layer (not shown) on the wall layer, the capping layer, the wall layer, and the functional surface 2a cooperate to form an internal space for accommodating the resonator 4, thereby constituting an elastic wave device 1 with a WLP (Wafer Level Package) structure.

[0041] The circuit pattern is typically formed on the functional surface 2a by a conductive metal layer 3 formed by photolithography.

[0042] Figures 7(a) and 7(b) are circuit diagrams illustrating an example of a circuit constructed including the circuit pattern described above. In these diagrams, reference numeral 5 indicates an input / output port, reference numeral 6 indicates ground, reference numeral 7 indicates a coil element described later, reference numeral 8 indicates wiring between resonators, and reference numeral 9 indicates external connection wiring.

[0043] In Figure 7(a), numeral 4a represents a resonator 4 connected in series, numeral 4b represents a resonator 4 connected in parallel, and coil element 7 is disposed between the resonator 4b connected in parallel and ground 6.

[0044] In Figure 7(b), reference numeral 4a represents a resonator 4 connected in series, reference numeral 4b represents a resonator 4 connected in parallel, and coil element 7 is disposed between the resonator 4a connected in series and the port 5.

[0045] like Figure 5 and Figure 6 As shown, the resonator 4 is constructed by arranging IDT electrodes 41 between the reflectors 40.

[0046] The IDT electrode 41 is composed of electrode pairs. Each electrode pair is formed by arranging multiple electrode fingers 41a in a parallel manner, which cross along the length direction of the main mode surface wave propagation direction x, and connecting them at one end of the electrode fingers 41a through a busbar 41b.

[0047] The IDT electrode 41 is connected to the outside at the busbar 41b, so it does not form a closed path.

[0048] On the other hand, in this embodiment, the two resonators 4b connected in parallel in the circuit shown in FIG7 are resonators 4′ with a special structure.

[0049] In the illustrated example, two uniquely structured resonators 4′ are arranged side by side in a direction orthogonal to the propagation direction x of the elastic surface wave.

[0050] In the resonator 4′ with its unique structure, such as Figure 5 and Figure 6 As shown, the reflector 40 has the following configuration: in the propagation direction x of the elastic surface wave excited by the IDT electrode 41, a plurality of reflector elements 40c are configured along the propagation direction x, consisting of two adjacent electrode fingers 40a extending in a direction orthogonal to the propagation direction x, and a first busbar 40b used only to connect the two electrode fingers 40a at one end.

[0051] In the illustrated example, each of the reflectors 40 clamping the IDT electrode 41 on the left and right sides comprises three reflector elements 40c. Adjacent reflector elements 40c are not connected to each other on the side forming the first busbar 40b, but are independent of each other.

[0052] Meanwhile, the reflector 40 also has the following configuration: in a second busbar 40d extending along the propagation direction x, the other ends of the two electrode fingers 40a of each of the plurality of reflector elements 40c are respectively connected.

[0053] The second busbar 40d has a length that spans the forming area of ​​a reflector 40.

[0054] Two electrode fingers 40a constituting a reflector element 40c are arranged side-by-side at a distance along the propagation direction x. One end of each electrode finger 40a lies on a virtual first straight line (not shown) extending along the propagation direction x, and the other end of each electrode finger 40a lies on a virtual second straight line (not shown) extending along the propagation direction x. That is, the two electrode fingers 40a constituting a reflector element 40c have the same length.

[0055] In addition, three reflector elements 40c are arranged side by side in the propagation direction x with spacing between them.

[0056] Meanwhile, on the side opposite to the side forming the first busbar 40b, the reflector 40 has a second busbar 40d that connects the three reflector elements 40c together by connecting the other ends of the two electrode fingers 40a that constitute the reflector element 40c.

[0057] That is, in the illustrated example, the reflector 40 consists of three reflector elements 40c and a second busbar 40d.

[0058] The reflector 40 thus constructed is not connected to the outside, but forms a closed path. However, in this embodiment, by constructing the reflector 40 as described above, consisting of a plurality of the reflector elements 40c connected by a second busbar 40d, it has been confirmed that even if the coil element 7 described later is placed close to its forming area, it will not cause a significant decrease in the coil Q value.

[0059] Therefore, in this embodiment, the reflector 40 in the resonator 4′ with the unique structure has an even number of electrode fingers 40a.

[0060] It should be noted that the resonator 4′ with its unique structure can be designed such that, in each of the two reflectors 40 constituting the resonator 4, the second busbar 40d is positioned on the same side of two boundaries along the propagation direction x in the forming region of the resonator 4 (see [reference]). Figure 6 ).

[0061] Alternatively, the resonator 4′ with a unique structure can also be designed such that, in one of the two reflectors 40 constituting the resonator 4, the second busbar 40d is positioned on one side of the two boundaries along the propagation direction x in the forming region of the resonator 4, while in the other of the two reflectors 40 constituting the resonator 4, the second busbar 40d is positioned on the other side of the two boundaries along the propagation direction x in the forming region of the resonator 4 (see...). Figure 5 ).

[0062] A coil element 7 made of conductive metal is integrated on the circuit pattern having the above-described configuration.

[0063] like Figure 3 As shown, the coil element 7 is located on a virtual first plane S1 along the surface of the conductive metal layer 3 constituting the circuit pattern (i.e., the surface opposite to the fixed side of the functional surface 2a of the device chip 2), and is configured such that its lower surface (i.e., the side 7g facing the functional surface 2a of the device chip 2) forms a virtual second plane S2 along a direction parallel to the first plane S1 and with a predetermined gap between it and the first plane S1 in a direction orthogonal to the functional surface 2a.

[0064] The surface of the conductive metal layer 3 is located in contact with the first plane S1, and the lower surface of the coil element 7 is located in contact with the second plane S2. An air gap is formed between the resonator 4′ and the coil element 7 at the upper portion 7a of the IDT electrode (described later) and the upper portion 7b of the reflector.

[0065] The distance between the first plane S1 and the second plane S2, considering the angle of forming an air gap between the resonator 4 and the coil element 7 while miniaturizing the elastic wave device 1 as much as possible, is preferably set to more than 0.5 μm and less than 3 μm.

[0066] Furthermore, the coil element 7 is configured to have: an upper IDT electrode portion 7a located above the formation region of the IDT electrode 41 in the resonator 4′ of the unique structure, and an upper reflector portion 7b located above the formation region of the reflector 40.

[0067] In this embodiment, the upper portion 7a of the IDT electrode in the coil element 7 is configured to extend along the propagation direction x of the elastic surface wave.

[0068] Additionally, the upper portion 7b of the reflector in the coil element 7 is configured to have a parallel portion 7c extending along the propagation direction x of the elastic surface wave, and a cross portion 7d orthogonal to the propagation direction x.

[0069] In this embodiment, the device chip 2 has a rectangular outline when viewed from a direction orthogonal to the functional surface 2a.

[0070] At the same time, such as Figure 2 As shown, the coil element 7, when viewed from a direction orthogonal to the functional surface 2a, is constructed as a square and a single-turn structure, and has two length side portions 7e arranged along the long side direction of the device chip 2, and two width side portions 7f arranged along the short side direction of the device chip 2.

[0071] In the illustrated example, the coil element 7 is connected in parallel in the circuit shown in FIG7 and is configured to position a portion of it above the forming regions of the two resonators 4′ having the specific structure.

[0072] In the illustrated example, the coil element 7 positions one of its length-side portions 7e in... Figure 2 The resonator 4' is positioned above the upper resonator, and the other side of its length side portion 7e is positioned in the middle. Figure 2 Above the resonator 4' located on the lower side, and simultaneously, through the resonator located on the lower side... Figure 2 The width portion 7f on the left connects one end of the two length portions 7e to each other, thus forming a square and one-turn structure.

[0073] In the illustrated example, the coil element 7 is composed of a linear body supported on the functional surface 2a of the device chip 2. The coil element 7 has a side 7g facing the functional surface 2a of the device chip 2, and another side 7h opposite to the side 7g, and its thickness is the distance between the two sides 7g and 7h.

[0074] In the illustrated example, the coil element 7 is located outside the formation region of the resonator 4 on the functional surface 2a of the device chip 2, and is supported by a pillar 10 erected on the functional surface 2a, so that an air gap is formed between it and the resonator 4.

[0075] Additionally, the coil element 7 is electrically connected to the resonator 4 via one of the pillars 10, thereby forming the circuit shown in FIG7.

[0076] Typically, the device chip 2 has a side dimension of 0.5 to 1 mm and a thickness of 0.15 to 0.2 mm.

[0077] In addition, the thickness of the conductive metal layer 3 is typically 0.15 to 0.5 μm.

[0078] Furthermore, the thickness of the coil element 7 is typically 2 to 5 μm, and its width is 20 to 50 μm.

[0079] It should be noted that, in order to facilitate understanding of the structure of the elastic wave device 1, the thickness of its constituent elements has been exaggerated in each figure.

[0080] as Figure 2 As shown, two resonators 4 are arranged side-by-side on the device chip 2 through a conductive metal layer 3, and a resonator is disposed on the forming area of ​​the chip. Figure 2 In the case of coil element 7 shown which is substantially the same as coil element 7, respectively for embodiments ( Figure 8 Comparative Example 1 Figure 9 ) and Comparative Example 2 ( Figure 10 A three-dimensional electromagnetic field simulation was performed, and the results are shown in Figure 11.

[0081] (Simulation conditions) The main simulation conditions are shown below.

[0082] Device chip 2 uses lithium tantalate with a thickness of 200 μm.

[0083] The conductive metal layer 3 is made of aluminum, with a thickness of 0.5 μm and a width of 1 μm. The spacing between adjacent conductive metal layers 3 is set to 1 μm.

[0084] In resonator 4, the formation area of ​​IDT electrode 41 is set to 210 μm × 280 μm, and the formation areas of the two reflectors 40 are set to 210 μm × 80 μm respectively. The two resonators 4 are arranged side by side with a 10 μm interval in a direction orthogonal to the propagation direction x of the elastic surface wave.

[0085] The coil element 7 is made of aluminum and has a single-turn structure with an outer dimension of 400 μm, a width of 20 μm, and a thickness of 2 μm. The coil element 7 is arranged with a 1.5 μm gap between it and the conductive metal layer 3.

[0086] The simulation was performed in 50 MHz increments across a frequency range of 100 MHz to 5 GHz.

[0087] (Experimental Example) like Figure 8 As shown in the embodiment, the reflectors 40 on both the left and right sides adopt a resonator 4′ with a special structure. In this resonator 4′ with a special structure, the three reflector elements 40c are connected through the second bus bar 40d (which is a configuration involved in the embodiment of the present invention).

[0088] In this case, the inductance value L of the coil is represented by a solid line in Figure 11(a), and the Q value of the coil is represented by a solid line in Figure 11(b).

[0089] (Comparative Example 1) like Figure 9 As shown, in Comparative Example 1, the reflectors 40 on both the left and right sides are all general resonators 4, which are configured such that a closed path is formed by connecting multiple electrode fingers 40a at one end using a bus bar 40e, and also connecting these electrode fingers 40a at the other end using a bus bar 40e.

[0090] In this case, the inductance value L of the coil is represented by a dashed line in Figure 11(a), and the Q value of the coil is represented by a dashed line in Figure 11(b).

[0091] (Comparative Example 2) like Figure 9 As shown, in Comparative Example 2, the reflectors 40 on both the left and right sides are configured such that the multiple electrode fingers 40a are arranged without being connected to each other.

[0092] In this case, the inductance value L of the coil is represented by a dashed line in Figure 11(a), and the Q value of the coil is represented by a dashed line in Figure 11(b).

[0093] Comparing the coil Q values ​​shown in Figure 11(b), it can be seen that the Q value of the embodiment is greater than that of Comparative Example 1 and slightly less than that of Comparative Example 2 across all frequency ranges. The coil inductance value L shown in Figure 11(a) also exhibits the same trend.

[0094] A comparison of the characteristics of three resonators 4 with different configurations of reflector 40 shows that the coil Q value exhibits the best value in Comparative Example 2. Since the multiple electrode fingers 40a of reflector 40 are not connected to each other, the reflection coefficient of reflector 40 in resonator 4 is small, which degrades the characteristics of resonator 4. Therefore, it is usually not used in practice.

[0095] In the reflector 40 of the embodiment, two adjacent electrode fingers 40a corresponding to an elastic surface wave wavelength are connected at one end, and all electrode fingers 40a are connected at the other end. Therefore, its reflection coefficient is comparable to that of the reflector 40 of Comparative Example 1. Thus, the characteristics of the resonator 4′ of the embodiment are comparable to those of the resonator 4 of Comparative Example 1.

[0096] As can be seen from the above results, compared with the resonator 4 of Comparative Example 1, which is usually used, the resonator 4′ in the embodiment maintains the same level in terms of the characteristics of the resonator 4, while the Q value of the coil element 7 arranged above it is significantly improved.

[0097] The above differences can be explained by the flow path of the eddies generated within the reflector 40 by the coil element 7 disposed on the reflector 40.

[0098] In Comparative Example 2, since there are no closed current paths within the reflector 40, eddy currents are not easily generated; while in Comparative Example 1, there are multiple closed current paths within the reflector 40, and the area within each closed current path is relatively large.

[0099] On the other hand, in the embodiment, although there is a closed current path within the reflector 40, the closed current path is limited to the area between the two electrode fingers 40a that constitute the reflector element 40c, so the area within its current path is very small.

[0100] Since the decrease in the inductance values ​​L and Q of the coil element 7 is caused by the reverse magnetic field generated in the coil element 7 as a result of eddy currents, the generated reverse magnetic field is reduced when the area in the eddy current path is small, thereby making the decrease in the inductance values ​​L and Q of the coil element 7 in the embodiment smaller.

[0101] It should be noted that in the above embodiments, the coil element 7 is constructed as a square and is a one-turn structure, but the coil element 7 may also be a structure with less than one turn or more than one turn; in addition, when viewed from a direction orthogonal to the functional surface 2a, at least a portion of the coil element 7 may also have a non-linear curved portion.

[0102] Furthermore, in the above embodiments, the coil element 7 is disposed above the two resonators 4', but the resonator 4' disposed below the coil element 7 via an air gap may be one or more; and a portion of the coil element 7 may also be located above the inter-resonator wiring or external connection wiring (not shown).

[0103] Of course, the present invention is not limited to the embodiments described above, but includes all embodiments that can achieve the purpose of the present invention.

Claims

1. An elastic wave device, characterized in that, include: A device chip having at least one functional surface made of piezoelectric material; A circuit pattern consisting of a conductive metal layer and containing multiple resonators, formed on the functional surface; And a coil element made of conductive metal, the coil element being located on a virtual first plane along the surface of the conductive metal layer, and being configured such that its lower surface is along a virtual second plane parallel to the first plane and forming a predetermined gap between the first plane; in, The resonator is constructed by arranging IDT electrodes between the reflectors; At least a portion of the resonators are resonators with a unique structure, which is configured in such a way that, in the propagation direction of the elastic surface wave excited by the IDT electrodes, a plurality of reflector elements are arranged along the propagation direction, each consisting of two adjacent electrode fingers extending in a direction orthogonal to the propagation direction and a first busbar connecting the two electrode fingers at one end; and, in a second busbar extending along the propagation direction, the other ends of the two electrode fingers of each of the plurality of reflector elements are respectively connected. and, The coil element is configured to have: an upper portion of the IDT electrode located above the IDT electrode forming region in the resonator of the unique structure, and an upper portion of the reflector located above the reflector forming region.

2. The elastic wave device according to claim 1, characterized in that, The upper portion of the IDT electrode in the coil element is configured to extend along the propagation direction of the elastic surface wave; and... The upper portion of the reflector in the coil element is configured to have a parallel portion extending along the propagation direction of the elastic surface wave, and an intersecting portion orthogonal to the propagation direction.

3. The elastic wave device according to claim 1, characterized in that, When viewed from a direction orthogonal to the functional plane, the device chip has a rectangular outline; and, When viewed from a direction orthogonal to the functional plane, the coil element is constructed as a square, single-turn structure, and has two length-side portions arranged along the long side of the device chip, and two width-side portions arranged along the short side of the device chip.

4. The elastic wave device according to claim 1, characterized in that, The distance between the first plane and the second plane is greater than 0.5 μm and less than 3 μm.

5. The elastic wave device according to claim 1, characterized in that, The reflector consists of three reflector elements and a second busbar.

6. The elastic wave device according to claim 1, characterized in that, The reflector is not connected to the outside, but forms a closed path.

7. The elastic wave device according to claim 1, characterized in that, The reflector as a whole has an even number of electrode fingers.

8. The elastic wave device according to claim 1, characterized in that, In one of the two reflectors constituting the resonator, the second busbar is positioned on one side of the two boundaries along the propagation direction x in the forming region of the resonator, while in the other of the two reflectors constituting the resonator, the second busbar is positioned on the other side of the two boundaries along the propagation direction x in the forming region of the resonator.

9. The elastic wave device according to claim 1, characterized in that, The thickness of the conductive metal layer is 0.15 to 0.5 μm.

10. The elastic wave device according to claim 1, characterized in that, The thickness of the coil element is 2 to 5 μm, and its width is 20 to 50 μm.

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