Josephson junction element, quantum device, and method for manufacturing a Josephson junction element

Abstract

This Josephson junction element has a first superconducting film, a first insulating film provided above the first superconducting film, and a second superconducting film provided above the first insulating film, wherein: a surface layer portion of the first insulating film has a first region, and a second region at the periphery of the first region; the electrical insulation of the first region is higher than the electrical insulation of the second region; and, in a plan view, the second superconducting film is on the inside of the boundary of the first region and the second region.

Description

Technical Field

[0004] , , ,

[0005] ,

[0001] The present disclosure relates to a Josephson junction device, a quantum device, and a method for manufacturing a Josephson junction device.

Background Art

[0002] Consideration has been given to the application of a quantum computer with qubits including Josephson junction devices. A Josephson junction device has two superconducting films and an insulating film therebetween.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0004] Conventionally, one of the superconducting films included in a Josephson junction device has been processed by reactive ion etching after film formation, and damage inevitably occurs in the vicinity of the side surface of the remaining superconducting film after processing. When damage occurs in the superconducting film, the characteristics of the Josephson junction between the damaged region and the other superconducting film may vary. Furthermore, damage inevitably occurs in the insulating film during reactive ion etching of the superconducting film. Even when the Josephson junction includes a region where damage has occurred in the insulating film, the characteristics of the Josephson junction may vary.

[0005] The object of this disclosure is to provide a Josephson junction element, a quantum device, and a method for manufacturing a Josephson junction element that can obtain stable characteristics. [Means for solving the problem]

[0006] According to one embodiment of the present disclosure, a Josephson junction element is provided, comprising a first superconducting film, a first insulating film provided on the first superconducting film, and a second superconducting film provided on the first insulating film, wherein the surface layer of the first insulating film has a first region and a second region surrounding the first region, the electrical insulation of the first region is higher than that of the second region, and in plan view, the second superconducting film is located inside the boundary between the first region and the second region. [Effects of the Invention]

[0007] According to this disclosure, stable characteristics can be obtained. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 is a cross-sectional view showing a Josephson junction element according to the first embodiment. [Figure 2] Figure 2 is a plan view showing a Josephson junction element according to the first embodiment. [Figure 3] Figure 3 is a cross-sectional view (part 1) showing a method for manufacturing a Josephson junction element according to the first embodiment. [Figure 4] Figure 4 is a cross-sectional view (part 2) showing a method for manufacturing a Josephson junction element according to the first embodiment. [Figure 5] Figure 5 is a cross-sectional view (part 3) showing a method for manufacturing a Josephson junction element according to the first embodiment. [Figure 6] Figure 6 is a cross-sectional view (part 4) showing a method for manufacturing a Josephson junction element according to the first embodiment. [Figure 7] Figure 7 is a cross-sectional view (part 5) showing a method for manufacturing a Josephson junction element according to the first embodiment. [Figure 8]FIG. 8 is a cross-sectional view (part 6) showing a method of manufacturing a Josephson junction element according to the first embodiment. [Figure 9] FIG. 9 is a cross-sectional view (part 7) showing a method of manufacturing a Josephson junction element according to the first embodiment. [Figure 10] FIG. 10 is a cross-sectional view (part 8) showing a method of manufacturing a Josephson junction element according to the first embodiment. [Figure 11] FIG. 11 is a cross-sectional view (part 9) showing a method of manufacturing a Josephson junction element according to the first embodiment. [Figure 12] FIG. 12 is a cross-sectional view (part 10) showing a method of manufacturing a Josephson junction element according to the first embodiment. [Figure 13] FIG. 13 is an enlarged cross-sectional view showing a part of FIG. 1. [Figure 14] FIG. 14 is a cross-sectional view showing a portion corresponding to FIG. 13 in a Josephson junction element according to a reference example. [Figure 15] FIG. 15 is a cross-sectional view showing a Josephson junction element according to the second embodiment. [Figure 16] FIG. 16 is a plan view showing a Josephson junction element according to the second embodiment. [Figure 17] FIG. 17 is a cross-sectional view (part 1) showing a method of manufacturing a Josephson junction element according to the second embodiment. [Figure 18] FIG. 18 is a cross-sectional view (part 2) showing a method of manufacturing a Josephson junction element according to the second embodiment. [Figure 19] FIG. 19 is a cross-sectional view (part 3) showing a method of manufacturing a Josephson junction element according to the second embodiment. [Figure 20] FIG. 20 is a cross-sectional view (part 4) showing a method of manufacturing a Josephson junction element according to the second embodiment. [Figure 21] FIG. 21 is a cross-sectional view (part 5) showing a method of manufacturing a Josephson junction element according to the second embodiment. [Figure 22] FIG. 22 is a cross-sectional view (part 6) showing a method of manufacturing a Josephson junction element according to the second embodiment. [Figure 23] FIG. 23 is a cross-sectional view (the seventh) showing a method for manufacturing a Josephson junction device according to the second embodiment. [Figure 24] FIG. 24 is a cross-sectional view (the eighth) showing a method for manufacturing a Josephson junction device according to the second embodiment. [Figure 25] FIG. 25 is a cross-sectional view (the ninth) showing a method for manufacturing a Josephson junction device according to the second embodiment. [Figure 26] FIG. 26 is a cross-sectional view (the tenth) showing a method for manufacturing a Josephson junction device according to the second embodiment. [Figure 27] FIG. 27 is a diagram showing a quantum device according to the third embodiment. MODE FOR CARRYING OUT THE INVENTION

[0009] Hereinafter, embodiments of the present disclosure will be specifically described with reference to the accompanying drawings. In the present specification and drawings, components having substantially the same functional configuration may be denoted by the same reference numerals, and redundant description may be omitted.

[0010] (First Embodiment) First, the first embodiment will be described. The first embodiment relates to a Josephson junction device. FIG. 1 is a cross-sectional view showing a Josephson junction device according to the first embodiment. FIG. 2 is a plan view showing a Josephson junction device according to the first embodiment. FIG. 1 corresponds to a cross-sectional view taken along line I-I in FIG. 2. In FIG. 2, the wiring 141, the wiring 142, and the insulating film 130 are omitted.

[0011] As shown in FIGS. 1 and 2, the Josephson junction device <0000xxx>100 according to the first embodiment mainly includes a substrate <0000xxx>110, a superconducting film <0000xxx>121, an insulating film <0000xxx>122, a superconducting film <0000xxx>123, an insulating film <0000xxx>130, a wiring <0000xxx>141, and a wiring <0000xxx>142.

[0012] The substrate 110 has, for example, a silicon (Si) substrate 111 and an insulating film 112. The insulating film 112 is formed on the silicon substrate 111. The insulating film 112 is, for example, a silicon oxide film. The substrate 110 is a so-called oxide-coated substrate. The superconducting film 121 is provided on the insulating film 112. The superconducting film 121 is, for example, a niobium (Nb) film with a thickness of about 200 nm. The insulating film 122 is provided on the superconducting film 121. The insulating film 122 is, for example, an aluminum oxide (Al) film with a thickness of about 20 nm. The superconducting film 123 is provided on the insulating film 122. The superconducting film 123 is, for example, a niobium film with a thickness of about 200 nm. The superconducting film 121 is an example of a first superconducting film, the insulating film 122 is an example of a first insulating film, and the superconducting film 123 is an example of a second superconducting film.

[0013] The surface layer of the insulating film 122 has a first region 122A and a second region 122B surrounding the first region 122A. The second region 122B is more damaged than the first region 122A, and its electrical insulation is lower than that of the first region 122A. In other words, the electrical insulation of the first region 122A is higher than that of the second region 122B. The superconducting film 123 is provided on top of the first region 122A. In a plan view, the superconducting film 123 is located inside the boundary between the first region 122A and the second region 122B. The magnitude of the damage in the first region 122A and the second region 122B can be determined, for example, using a transmission electron microscope (TEM). That is, in TEM observation, the phase contrast differs between the region with large damage and the region with small damage, so the first region 122A and the second region 122B can be distinguished.

[0014] A groove 121Z is formed in the superconducting film 121, and a groove 122Z is ​​formed in the insulating film 122. Groove 122Z is ​​connected to groove 121Z, and the insulating film 112 is exposed through grooves 121Z and 122Z. Grooves 121Z and 122Z are, for example, grooves for device isolation. The insulating film 130 covers the substrate 110, the superconducting film 121, the insulating film 122, and the superconducting film 123. The insulating film 130 is, for example, a silicon oxide film.

[0015] Contact holes 122X are formed in the insulating film 122, and contact holes 130X are formed in the insulating film 130. The contact holes 130X are connected to the contact holes 122X, and the superconducting film 121 is exposed through the contact holes 122X and 130X. The contact holes 122X penetrate, for example, the second region 122B. The wiring 141 is provided on the insulating film 130 and is in contact with the superconducting film 121 through the contact holes 122X and 130X. The wiring 141 is, for example, a niobium film.

[0016] A contact hole 130Y is formed in the insulating film 130. The superconducting film 123 is exposed through the contact hole 130Y. A recess 123Y connected to the contact hole 130Y may be formed on the surface of the superconducting film 123. The wiring 142 is provided on the insulating film 130 and is in contact with the superconducting film 123 through the contact hole 130Y. The wiring 142 is, for example, a niobium film.

[0017] Next, a method for manufacturing the Josephson junction element 100 according to the first embodiment will be described. Figures 3 to 12 are cross-sectional views showing the method for manufacturing the Josephson junction element according to the first embodiment.

[0018] First, as shown in Figure 3, a substrate 110 having a silicon substrate 111 and an insulating film 112 is prepared, and a superconducting film 121, an insulating film 122, and a superconducting film 123 are formed on the insulating film 112.

[0019] Next, as shown in Figure 4, a resist pattern 191 is formed on the superconducting film 123. The resist pattern 191 has an opening 191X. In a plan view, the opening 191X generally overlaps with the region where the second region 122B of the insulating film 122 is formed.

[0020] Subsequently, as shown in Figure 5, the superconducting film 123 is etched using the resist pattern 191 as a mask. This etching is reactive ion etching (RIE) using a reactive gas 150 mainly composed of sulfur hexafluoride (SF6), for example. This etching is carried out until the insulating film 122 is exposed. As a result, the portion of the superconducting film 123 that was covered by the resist pattern 191 remains. The vicinity of the remaining side surface of the superconducting film 123 is damaged by etching, and a damaged region 123B is formed near the side surface of the superconducting film 123. The superconducting film 123 has an internal region 123A that is not damaged by etching inside the damaged region 123B. In addition, the vicinity of the upper surface of the insulating film 122 is also damaged by etching, and a first region 122A and a second region 122B surrounding the first region 122A are formed on the surface layer of the insulating film 122. The second region 122B experiences greater etching damage than the first region 122A, resulting in lower electrical insulation properties for the second region 122B compared to the first region 122A. The first region 122A is formed inside the outer edge of the resist pattern 191 in a plan view.

[0021] Next, as shown in Figure 6, the resist pattern 191 is removed. Then, the damaged region 123B is removed by etching the superconducting film 123. This etching is isotropic etching, such as wet etching. For example, the superconducting film 123 is etched by about 20 nm in a direction parallel to the surface of the substrate 110. In other words, the superconducting film 123 is reduced in size in a plan view by isotropic etching. As a result, the superconducting film 123 is located on the first region 122A and, in a plan view, is located inside the boundary between the first region 122A and the second region 122B. If the material of the superconducting film 123 is niobium, for example, an HF solution, a mixed solution of HF and H2O2, a mixed solution of HF, H2SO4 and HNO3, or a mixed solution of HF and HNO3 can be used as the etchant. If the material of the superconducting film 123 is aluminum, for example, a diluted HCl solution or a diluted H2SO4 solution can be used as the etchant.

[0022] Subsequently, as shown in Figure 7, a resist pattern 192 is formed on the insulating film 122 and the superconducting film 123. The resist pattern 192 has an opening 192Z. In a plan view, the opening 192Z overlaps with the region where grooves 121Z and 122Z are formed.

[0023] Next, as shown in Figure 8, the insulating film 122 is milled using the resist pattern 192 as a mask. As a result, grooves 122Z are formed in the insulating film 122. Furthermore, the superconducting film 123 is etched using the resist pattern 192 as a mask. This etching is performed using RIE, for example, with a reactive gas mainly composed of sulfur hexafluoride. As a result, grooves 121Z are formed in the superconducting film 121.

[0024] Next, as shown in Figure 9, the resist pattern 192 is removed. Then, an insulating film 130 is formed to cover the substrate 110, the superconducting film 121, the insulating film 122, and the superconducting film 123. The insulating film 130 is formed, for example, by chemical vapor deposition (CVD).

[0025] Next, as shown in Figure 10, a resist pattern 193 is formed on the insulating film 130. The resist pattern 193 has openings 193X and 193Y. In a plan view, opening 193X overlaps with the region where contact holes 122X and 130X are formed, and opening 193Y overlaps with the region where contact hole 130Y is formed.

[0026] Next, as shown in Figure 11, etching of the insulating film 130 is performed using the resist pattern 193 as a mask. This etching is RIE using a reactive gas mainly composed of fluorocarbon (CF4), for example. As a result, contact holes 130X and 130Y are formed in the insulating film 130. Furthermore, milling of the insulating film 122 is performed using the resist pattern 193 as a mask. As a result, contact holes 130X are formed in the insulating film 122. At this time, recesses 123Y may be formed in the portion of the superconducting film 123 exposed from the contact holes 130Y.

[0027] Subsequently, as shown in Figure 12, wiring 141 that contacts the superconducting film 121 through contact holes 122X and 130X, and wiring 142 that contacts the superconducting film 123 through contact hole 130Y are formed on the insulating film 130.

[0028] In this way, the Josephson junction element 100 according to the first embodiment can be manufactured. As the Josephson junction element is miniaturized, the proportion of the region where damage occurs in the superconducting film increases, which may lead to a significant change in properties. Therefore, the present invention is particularly effective in such cases.

[0029] Here, the effects obtained by the Josephson junction element 100 according to the first embodiment will be explained in comparison with the reference example. Figure 13 is a cross-sectional view showing an enlarged portion of Figure 1. Figure 14 is a cross-sectional view showing the portion of the Josephson junction element according to the reference example that corresponds to Figure 13.

[0030] As shown in Figure 13, the surface layer of the insulating film 122 has a first region 122A and a second region 122B. The second region 122B is damaged by RIE (see Figure 5), while the first region 122A is not. In other words, the second region 122B is more damaged than the first region 122A. In the first embodiment, in a plan view, the superconducting film 123 is located inside the boundary between the first region 122A and the second region 122B. Therefore, the Josephson junction 100A between the superconducting film 121 and the superconducting film 123 is separated from the second region 122B. For this reason, stable properties can be obtained according to the first embodiment.

[0031] On the other hand, as shown in Figure 14, in the reference example, the superconducting film 123 includes a damaged region 123B, and in a plan view, the superconducting film 123 straddles the boundary between the first region 122A and the second region 122B, and includes the portion outside this boundary. Between the superconducting film 121 and the superconducting film 123, in addition to the Josephson junction 100A that is away from the second region 122B, there is also a Josephson junction 100B that includes the second region 122B. Furthermore, the Josephson junction 100B may also be the Josephson junction between the superconducting film 121 and the damaged region 123B. Therefore, in the reference example, the properties are prone to variation.

[0032] (Second Embodiment) Next, a second embodiment will be described. The second embodiment relates to a Josephson junction element. Figure 15 is a cross-sectional view showing a Josephson junction element according to the second embodiment. Figure 16 is a plan view showing a Josephson junction element according to the second embodiment. Figure 15 corresponds to a cross-sectional view along the line XV-XV in Figure 16. In Figure 16, wiring 141, wiring 142 and insulating film 130 are omitted.

[0033] As shown in Figures 15 and 16, the Josephson junction element 200 according to the second embodiment mainly comprises a substrate 110, a superconducting film 121, an insulating film 122, a superconducting film 123, an insulating film 224, an insulating film 130, wiring 141, and wiring 142.

[0034] The insulating film 224 is provided on top of the superconducting film 123. The insulating film 224 is, for example, an aluminum oxide film with a thickness of about 20 nm. In other words, the material of the insulating film 224 is the same as the material of the insulating film 122, and the thickness of the insulating film 224 is equal to the thickness of the insulating film 122. The insulating film 224 is an example of a second insulating film.

[0035] The insulating film 130 covers the substrate 110, the superconducting film 121, the insulating film 122, the superconducting film 123, and the insulating film 224. The insulating film 130 is an example of a third insulating film.

[0036] Contact holes 122X are formed in the insulating film 122, and contact holes 130X are formed in the insulating film 130. Contact holes 130X are connected to contact holes 122X, and the superconducting film 121 is exposed through contact holes 122X and 130X. Contact holes 122X penetrate, for example, the second region 122B. Wiring 141 is provided on the insulating film 130 and is in contact with the superconducting film 121 through contact holes 122X and 130X. Wiring 141 is an example of a first wiring. Contact holes 122X and 130X are examples of a first opening.

[0037] Contact holes 224Y are formed in the insulating film 224. Contact holes 130Y are connected to contact holes 224Y, and the superconducting film 123 is exposed through contact holes 224Y and 130Y. In this embodiment, no recesses 123Y are formed on the surface of the superconducting film 123, and the surface of the superconducting film 123 is flat. Wiring 142 is provided on the insulating film 130 and is in contact with the superconducting film 123 through contact holes 224Y and 130Y. Wiring 142 is an example of a second wiring. Contact holes 224Y and 130Y are examples of a second opening.

[0038] The other configurations are the same as in the first embodiment.

[0039] Next, a method for manufacturing the Josephson junction element 200 according to the second embodiment will be described. Figures 17 to 26 are cross-sectional views showing the method for manufacturing the Josephson junction element according to the second embodiment.

[0040] First, as shown in Figure 17, a substrate 110 having a silicon substrate 111 and an insulating film 112 is prepared, and a superconducting film 121, an insulating film 122, a superconducting film 123, and an insulating film are formed on the insulating film 112.

[0041] Next, as shown in Figure 18, a resist pattern 191 is formed on the insulating film 224. The resist pattern 191 has an opening 191X. In a plan view, the opening 191X generally overlaps with the region where the second region 122B of the insulating film 122 is formed.

[0042] Subsequently, as shown in Figure 19, the insulating film 224 is milled using the resist pattern 191 as a mask. Furthermore, the superconducting film 123 is etched in the same manner as in the first embodiment. As a result, a damaged region 123B is formed near the side surface of the superconducting film 123. The superconducting film 123 has an internal region 123A that is not damaged by etching, inside the damaged region 123B. In addition, a first region 122A and a second region 122B surrounding the first region 122A are formed on the surface layer of the insulating film 122.

[0043] Next, as shown in Figure 20, the resist pattern 191 is removed. Then, similar to the first embodiment, the damaged region 123B is removed by isotropic etching of the superconducting film 123. In other words, the superconducting film 123 is reduced in size in a plan view by isotropic etching. As a result, the superconducting film 123 is located on the first region 122A and, in a plan view, is located inside the boundary between the first region 122A and the second region 122B.

[0044] Subsequently, as shown in Figure 21, a resist pattern 192 is formed on the insulating film 122, the superconducting film 123, and the insulating film 224. The resist pattern 192 has an opening 192Z. In a plan view, the opening 192Z overlaps with the region where grooves 121Z and 122Z are formed.

[0045] Next, as shown in Figure 22, the insulating film 122 is milled using the resist pattern 192 as a mask, similar to the first embodiment. As a result, grooves 122Z are formed in the insulating film 122. Furthermore, the superconducting film 123 is etched using the resist pattern 192 as a mask, similar to the first embodiment. As a result, grooves 121Z are formed in the superconducting film 121.

[0046] Next, as shown in Figure 23, the resist pattern 192 is removed. Then, an insulating film 130 is formed to cover the substrate 110, the superconducting film 121, the insulating film 122, the superconducting film 123, and the insulating film 224. The insulating film 130 is formed, for example, by the CVD method.

[0047] Next, as shown in Figure 24, a resist pattern 193 is formed on the insulating film 130, similar to the first embodiment. The resist pattern 193 includes openings 193X and 193Y. In a plan view, opening 193X overlaps with the region where contact holes 122X and 130X are formed, and opening 193Y overlaps with the region where contact holes 224Y and 130Y are formed.

[0048] Next, as shown in Figure 25, etching of the insulating film 130 is performed using the resist pattern 193 as a mask, similar to the first embodiment. As a result, contact holes 130X and 130Y are formed in the insulating film 130. Furthermore, milling of insulating films 122 and 224 is performed using the resist pattern 193 as a mask. As a result, contact holes 130X are formed in the insulating film 122 and contact holes 130Y are formed in the insulating film 224. Since the material of insulating film 224 is the same as the material of insulating film 122, and the thickness of insulating film 224 is equal to the thickness of insulating film 122, if milling of insulating film 122 is stopped when the superconducting film 121 is exposed, milling of insulating film 224 will also stop when the superconducting film 123 is exposed.

[0049] Subsequently, as shown in Figure 26, wiring 141 that contacts the superconducting film 121 through contact holes 122X and 130X, and wiring 142 that contacts the superconducting film 123 through contact holes 224Y and 130Y are formed on the insulating film 130.

[0050] In this way, the Josephson junction element 200 according to the second embodiment can be manufactured.

[0051] The same effects as the first embodiment can be obtained with the second embodiment. Furthermore, in the second embodiment, the formation of recesses 123Y on the surface of the superconducting film 123 can be suppressed. Therefore, damage to the superconducting film 123 associated with the formation of recesses 123Y can be suppressed.

[0052] It is desirable that the thickness of the insulating film 224 matches the thickness of the insulating film 122, but the insulating film 224 may be thicker or thinner than the insulating film 122. Also, it is desirable that the material of the insulating film 224 be the same as the material of the insulating film 122, but it is not necessarily required. In any case, it is desirable that the timing difference between the completion of milling of the insulating film 224 and the milling of the insulating film 122 be small.

[0053] The materials of the superconducting films 121 and 123 are not particularly limited and may include, for example, niobium, aluminum, niobium nitride, or titanium nitride, or any combination thereof. Similarly, the materials of the insulating films 122 and 224 are not particularly limited and may include aluminum oxide, aluminum nitride, hafnium oxide, or yttrium oxide, or any combination thereof.

[0054] (Third embodiment) Next, a third embodiment will be described. The third embodiment relates to a quantum device. Figure 27 is a diagram showing a quantum device according to the third embodiment.

[0055] The quantum device 300 according to the third embodiment includes a qubit 310, a readout circuit 320, and wirings 331 and 332. The qubit 310 includes Josephson junction elements 311, 312, and 313. The readout circuit 320 includes Josephson junction elements 321 and 322. The readout circuit 320 is connected between wirings 331 and 332. The qubit 310 is located inside the readout circuit 320. The readout circuit 320 reads the state of the qubit 310. The Josephson junction elements 311, 312, 313, 321, and 322 are Josephson junction elements 100 or 200.

[0056] According to the quantum device 300 of the third embodiment, stable characteristics can be obtained because it includes a Josephson junction element 100 or 200. The quantum device 300 can be used, for example, in a quantum computer.

[0057] Although preferred embodiments have been described in detail above, the invention is not limited to the embodiments described above, and various modifications and substitutions can be made to the embodiments described above without departing from the scope of the claims. [Explanation of symbols]

[0058] 100, 200, 311, 312, 313, 321, 322: Josephson junction elements 121, 123, Superconducting film 122, 130, 224: Insulating film 122A: 1st area 122B:Second area 123A: Internal area 123B: Damage Area 123Y: Recess 122X, 130X, 130Y, 224Y: Contact holes 141, 142: Wiring 300: Quantum devices 310: Quantum bit 320: Readout circuit

Claims

1. The first superconducting film and, A first insulating film provided on the first superconducting film, A second superconducting film provided on the first insulating film, It has, The surface layer of the first insulating film is The first area and, The second region surrounding the first region, It has, The electrical insulation of the first region is higher than that of the second region. A Josephson junction element characterized in that, in a plan view, the second superconducting film lies inside the boundary between the first region and the second region.

2. A second insulating film provided on the second superconducting film, The first insulating film, the second superconducting film, and the third insulating film covering the second insulating film, It has, A first opening reaching the first superconducting film is formed in the first insulating film and the third insulating film. A second opening reaching the second superconducting film is formed in the second insulating film and the third insulating film. A first wiring connected to the first superconducting film through the first opening, A second wiring connected to the second superconducting film through the second opening, A Josephson junction element according to claim 1, characterized by having the following features.

3. The material of the second insulating film is the same as the material of the first insulating film. The Josephson junction element according to claim 2, characterized in that the thickness of the second insulating film is equal to the thickness of the first insulating film.

4. The Josephson junction element according to claim 2 or 3, characterized in that, in a plan view, the second superconducting film is located inside the outer edge of the second insulating film.

5. A quantum device having a Josephson junction element, The Josephson junction device is The first superconducting film and, A first insulating film provided on the first superconducting film, A second superconducting film provided on the first insulating film, It has, The surface layer of the first insulating film is The first area and, The second region surrounding the first region, It has, The electrical insulation of the first region is higher than that of the second region. A quantum device characterized in that, in a plan view, the second superconducting film lies inside the boundary between the first region and the second region.

6. A second insulating film provided on the second superconducting film, The first insulating film, the second superconducting film, and the third insulating film covering the second insulating film, It has, A first opening reaching the first superconducting film is formed in the first insulating film and the third insulating film. A second opening reaching the second superconducting film is formed in the second insulating film and the third insulating film. A first wiring connected to the first superconducting film through the first opening, A second wiring connected to the second superconducting film through the second opening, The quantum device according to claim 5, characterized by having the following features.

7. The material of the second insulating film is the same as the material of the first insulating film. The quantum device according to claim 6, characterized in that the thickness of the second insulating film is equal to the thickness of the first insulating film.

8. The quantum device according to claim 6 or 7, characterized in that, in a plan view, the second superconducting film is located inside the outer edge of the second insulating film.

9. A step of providing a first insulating film on a first superconducting film, A step of providing a second superconducting film on the first insulating film, A step of processing the second superconducting film by reactive ion etching, A step of etching the sidewall of the processed second superconducting film, A method for manufacturing a Josephson junction element, characterized by having the following features.

10. Between the step of providing the second superconducting film and the step of processing the second superconducting film, The steps include providing a second insulating film on the second superconducting film, The process of processing the second insulating film, It has, After the step of etching the sidewall of the second superconducting film, A step of providing the first insulating film, the second superconducting film, and a third insulating film covering the second insulating film, The process involves forming a first opening in the first insulating film and the third insulating film that reaches the first superconducting film, and forming a second opening in the second insulating film and the third insulating film that reaches the second superconducting film, The process involves providing a first wiring connected to the first superconducting film through the first opening, and a second wiring connected to the second superconducting film through the second opening. A method for manufacturing a Josephson junction element according to claim 9, characterized by having the following features.

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