Gas sensor

Abstract

A gas sensor 100 comprises: a laminate 11 obtained by alternately laminating electrode layers 31, 32L and an insulation layer 24L; and a sensitive film 40 that reacts to a gas to be measured. A recess 11A1 recessed in the lamination direction is formed in the laminate 11. The recess 11A1 includes a side surface 11C including end surfaces of the electrode layers 31, 32L and an end surface of the insulation layer 24L. The sensitive film 40 is, within the side surface 11C of the recess 11A1, in contact with one insulation layer 24L and at least the pair of electrode layers 31, 32L sandwiching that insulation layer 24L.

Description

Gas Sensor

[0001] The present disclosure relates to gas sensors.

[0002] A conventional sensor technology is disclosed in Patent Document 1. Specifically, Patent Document 1 discloses a sensor in which a first Au layer is formed on a silicon substrate and an Al ２ O ３ By using the Al ２ O ３ The sensor has a nanogap with a thickness of 1000 nm. When a solution is injected into the nanogap, the sensor can detect a specific substance through a change in the electrical properties at both ends of the nanogap.

[0003] Japanese Patent Application Laid-Open No. 2006-234799

[0004] In the configuration disclosed in Patent Document 1, it is desirable to improve the detection sensitivity for a specific substance. To this end, it is conceivable to provide a sensor with, for example, a sensitive layer (sensitive film) that is in contact with two electrode layers (metal layers) and the insulating layer between them and reacts to a specific substance. However, in this case, the sensitive layer may become uneven or bent to conform to the shapes of the electrode layers or insulating layers, which may result in cracks or fractures in the uneven portions (this is called a step break).

[0005] The present disclosure is a technology completed in light of the above circumstances, and has an object to provide a gas sensor that can improve detection sensitivity and can suppress disconnection.

[0006] The gas sensor of the present disclosure is a gas sensor comprising a laminate in which electrode layers and insulating layers are alternately stacked, and a sensitive film that reacts to the gas to be measured, wherein the laminate has a recess that is recessed in the stacking direction, and the recess has side surfaces that include the end faces of the electrode layers and the end faces of the insulating layers, and the sensitive film is in contact with one insulating layer and at least a pair of electrode layers that sandwich it on the side surfaces of the recess.

[0007] According to the present disclosure, it is possible to provide a gas sensor that can improve detection sensitivity and that can suppress disconnection.

[0008] 1 is a plan view showing a schematic representation of a gas sensor device according to a first embodiment; 2 is a view showing a cross-sectional configuration of a portion of a gas sensor; 3 is an enlarged cross-sectional view of the vicinity of one inclined surface of a laminate; 4 is a partially enlarged plan view of a surface of a laminate; 5 is a plan view showing a schematic representation of a gas sensor device according to a second embodiment;

[0009] First, embodiments of the present disclosure will be described. (1) A gas sensor according to the present disclosure includes a laminate in which electrode layers and insulating layers are alternately stacked, and a sensitive film that reacts to a gas to be measured, wherein the laminate has a recess that is recessed in the stacking direction, the recess has side surfaces that include end faces of the electrode layers and the insulating layers, and the sensitive film is in contact with one insulating layer and at least a pair of electrode layers sandwiching the insulating layer on the side surfaces of the recess.

[0010] (2) In the gas sensor described in (1), a side surface of the recess may be inclined with respect to the stacking direction.

[0011] (3) In the gas sensor described in (1) or (2), the recess may have a bottom surface formed by a surface perpendicular to the stacking direction of the electrode layer, and the sensitive film may be in contact with the bottom surface of the recess.

[0012] (4) In the gas sensor according to any one of (1) to (3), the recess may have an outer shape that is a regular hexagon, a circle, an equilateral triangle, or a rhombus in plan view.

[0013] (5) In the gas sensor according to any one of (1) to (4), the recesses may be arranged in a closest-packed manner in a plan view.

[0014] <Embodiment 1> Embodiment 1 of the present disclosure will be described with reference to FIG. 1 and other figures. In this embodiment, a gas sensor 100 capable of detecting a specific gas (measurement gas) is illustrated. In FIGS. 2 and 3, the Z direction is the stacking direction, and the X direction perpendicular to the Z direction is the horizontal direction. The front side of the paper in FIGS. 1 and 4 and the upper side of the paper in FIGS. 2 and 3 are the front side (upper side in the stacking direction) of the gas sensor 100, and the back side of the paper in FIGS. 1 and 4 and the lower side of the paper in FIGS. 2 and 3 are the back side (lower side in the stacking direction) of the gas sensor 100.

[0015] 1 , the gas sensor 100 includes a flat substrate 10, a laminate 11 laminated on the surface of the substrate 10, and a first wiring 15 and a second wiring 16 disposed on the surface of the substrate 10 and connected to the laminate 11. The substrate 10 is made of, for example, silicon. The gas sensor 100, together with a power source 2 and an ammeter 3, constitutes a gas sensor device 1. The power source 2 is connected to the first wiring 15 and the ammeter 3. The ammeter 3 is connected to the second wiring 16.

[0016] 2 , the laminate 11 includes a plurality of electrode layers 31, 32L, and 32R and a plurality of insulating layers 21, 22, 23, 24L and 24R, and 25L and 25R stacked in a stacking direction (vertical direction). Specifically, a first insulating layer 21, a second insulating layer 22, and a third insulating layer 23 are stacked in this order on the surface of the substrate 10. A first electrode layer 31, a fourth insulating layer 24L and 24R, a second electrode layer 32L and 32R, and a fifth insulating layer 25L and 25R are stacked in this order on the surface of the third insulating layer 23. For the layers from the third insulating layer 23 to the fifth insulating layer 25L and 25R, the plurality of insulating layers 23, 24L and 24R, 25L and 25R, and the plurality of electrode layers 31, 32L, and 32R are stacked alternately in the stacking direction.

[0017] The fourth insulating layers 24L and 24R, the second electrode layers 32L and 32R, and the fifth insulating layers 25L and 25R each include a layer 24L, 32L, or 25L arranged on the left side of the paper relative to a first horizontal surface 11B (described later), and a layer 24R, 32R, or 25R arranged on the right side of the paper relative to the first horizontal surface 11B. The first electrode layer 31, the left fourth insulating layer 24L, and the left second electrode layer 32L are referred to as one main layer portion 12L. The first electrode layer 31, the right fourth insulating layer 24R, and the right second electrode layer 32R are referred to as the other main layer portion 12R.

[0018] In the stacking direction, the distance between the first electrode layer 31 and the left-side second electrode layer 32L (the thickness of the left-side fourth insulating layer 24L) and the distance between the first electrode layer 31 and the right-side second electrode layer 32R (the thickness of the right-side fourth insulating layer 24R) are each on the order of nanometers. These distances may be, for example, 1 nm or more and less than 1000 nm, less than 100 nm, or several tens of nm. The first electrode layer 31 is connected to the first wiring 15 shown in FIG. 1 . The second electrode layers 32L and 32R are each connected to the second wiring 16.

[0019] The materials for the electrode layers 31, 32L, and 32R and the wirings 15 and 16 are not particularly limited, but may be conductive materials, such as one or more metals such as aluminum, copper, gold, and platinum. The materials for the insulating layers 21, 22, 23, 24L and 24R, 25L, and 25R are not particularly limited, but may be non-conductive materials, such as compounds such as SiO2 and Si3N4. A heater 50 capable of heating the laminate 11 is provided inside the second insulating layer 22.

[0020] The surface 11A of the laminate 11 includes a first horizontal surface 11B, which is a surface extending perpendicular to the stacking direction (horizontally), second horizontal surfaces 11D and 11F, which are also surfaces extending perpendicular to the stacking direction and arranged above the first horizontal surface 11B, and inclined surfaces 11C and 11E, which are surfaces continuing from the first horizontal surface 11B and the second horizontal surfaces 11D and 11F, respectively, and which are surfaces inclined with respect to the stacking direction. The first horizontal surface 11B and the inclined surfaces 11C and 11E form a recess 11A1 recessed in the stacking direction from the second horizontal surfaces 11D and 11F in the laminate 11. The inclined surfaces 11C and 11E and the second horizontal surfaces 11D and 11F each include one surface 11C and 11D arranged on the left side of the first horizontal surface 11B in the drawing and the other surface 11E and 11F arranged on the right side of the first horizontal surface 11B in the drawing.

[0021] On the left inclined surface (side surface) 11C of the recess 11A1, the first electrode layer 31 and the left second electrode layer 32L are a pair of electrode layers sandwiching the left fourth insulating layer (single insulating layer) 24L. Similarly, on the right inclined surface (side surface) 11E of the recess 11A1, the first electrode layer 31 and the right second electrode layer 32R are a pair of electrode layers sandwiching the right fourth insulating layer (single insulating layer) 24R.

[0022] The first electrode layer 31 includes a thin layer portion 36, thick layer portions 38R and 38L that are thicker than the thin layer portion 36, and gradually varying layer portions 37R and 37L that are disposed between the thin layer portion 36 and the thick layer portions 38R and 38L and whose thickness gradually varies in the horizontal direction. The thick layer portions 38R and 38L are thicker than the second electrode layers 32R and 32L. The gradually varying layer portions 37R and 37L and the thick layer portions 38R and 38L each include one layer portion 37L and 38L disposed to the left of the thin layer portion 36 on the paper surface, and the other layer portion 37R and 38R disposed to the right of the thin layer portion 36 on the paper surface. A left-side fourth insulating layer 24L is laminated on a surface 38LA of the left-side thick layer portion 38L. Similarly, a right-side fourth insulating layer 24R is laminated on a surface 38RA of the right-side thick layer portion 38R.

[0023] The first horizontal surface 11B is a surface perpendicular to the stacking direction of the first electrode layer 31 and serves as the surface (top surface) of the thin layer portion 36. The first horizontal surface 11B also serves as the bottom surface of the recess 11A1. The second horizontal surfaces 11D and 11F serve as the surfaces (top surfaces) of the fifth insulating layers 25L and 25R, respectively.

[0024] The inclined surfaces 11C and 11E are the side surfaces of the recess 11A1 and are inclined with respect to the stacking direction. As shown in FIG. 3 , one of the inclined surfaces 11C is the side surface of the first electrode layer 31, and is a surface formed by connecting the side surface 37LA of the left gradually-changing layer portion 37L, the side surface 24LA of the left fourth insulating layer 24L, the side surface 32LA of the left second electrode layer 32L, and the side surface 25LA of the left fifth insulating layer 25. The side surfaces 37LA, 24LA, 32LA, and 25LA of each layer are sometimes referred to as end surfaces. The left side surface (inclined surface 11C) of the recess 11A1 includes the end surfaces 37LA and 32LA of the electrode layers (the first electrode layer 31 and the left second electrode layer 32L) and the end surface 24LA of the insulating layer (the left fourth insulating layer 24L). These end faces 37LA, 24LA, and 32LA form the side faces (end faces) of one of the main body layer portions 12L.

[0025] The first electrode layer 31 is the lowest layer of the main layer portions 12L, 12R and is considered a specific electrode layer having a first horizontal surface 11B that is continuous with the inclined surfaces 11C, 11E. The first electrode layer 31 as a specific electrode layer has a side surface 37LA of the left gradually changing layer portion 37L, which rises at an angle from its own first horizontal surface 11B and forms a part of one of the inclined surfaces 11C. The angle θ of the corner 39 formed by the first horizontal surface 11B and one of the inclined surfaces 11C (or the side surface 37LA) is an obtuse angle greater than 90 degrees. The configuration of one of the inclined surfaces 11C described above is the same (bilaterally symmetrical) as that of the other inclined surface 11E.

[0026] 2 and 3 , the gas sensor 100 includes a sensitive film 40 that contacts the bottom surface 11B of the recess 11A1, the side surfaces 11C and 11E of the recess 11A1, and the outer surfaces (second horizontal surfaces 11D and 11F) of the recess 11A1. The sensitive film 40 contacts the entire surface 11A of the laminate 11. On the side surfaces 11C and 11E of the recess 11A1, the sensitive film 40 contacts the side surface 24LA of the insulating layer 24L (or 24R) and the side surfaces 37LA and 32LA of at least one pair of electrode layers 31 and 32L (or 31 and 32R) that sandwich the side surface 24LA. The sensitive film 40 contacts the side surface 37LA of the left gradually changing layer portion 37L (the portion of one inclined surface 11C that connects to the first horizontal surface 11B) from the first horizontal surface 11B. The sensitive film 40 is in contact with the corner 39. Furthermore, the sensitive film 40 is in contact with the inclined surface 11C and the second horizontal surface 11D. This configuration is the same (symmetrical) on the other inclined surface 11E.

[0027] 4 shows a partially enlarged plan view of the surface 11A of the laminate 11, with the sensitive film 40 omitted. The recess 11A1 has a regular hexagonal outer shape in plan view. Specifically, the recess 11A1 includes a regular hexagonal bottom surface 11B in plan view and six inclined surfaces 11C, 11C1, 11C2, 11E, 11E1, and 11E2 that rise from six ends of the bottom surface 11B and extend at an angle relative to the stacking direction. The inclined surfaces 11C and 11E, the inclined surfaces 11C1 and 11E1, and the inclined surfaces 11C2 and 11E2 are arranged in pairs at both ends of the bottom surface 11B, respectively. The upper ends G1, G2, G3, G4, G5, and G6 of the inclined surfaces 11C, 11C1, 11C2, 11E, 11E1, and 11E2 form the outer shape of the recess 11A1, and as a whole form a regular hexagon in plan view.

[0028] On the surface 11A of the laminate 11, the plurality of recesses 11A1 are arranged in a close-packed manner in a plan view, and in this embodiment, are arranged in a honeycomb shape in a plan view. Specifically, the plurality of recesses 11A1 are arranged so that the distance between adjacent recesses 11A1 is equal to the distance between other adjacent recesses 11A1. For example, the distance L1 between a recess 11A1 arranged slightly above the center of the paper and the recess 11A1 arranged below it (slightly below the center of the paper) is equal to the distance L2 between the recess 11A1 arranged slightly above the center of the paper and the recess 11A1 arranged below and to the right of it (to the right of the center of the paper).

[0029] The sensitive film 40 contacts the recesses 11A1 and the surfaces between them (the second horizontal surfaces 11D, 11F, etc.). The sensitive film 40 also contacts the first horizontal surface 11B and the inclined surfaces 11C, 11C1, 11C2, 11E, 11E1, and 11E2 of the recess 11A1.

[0030] The sensitive film 40 is configured such that its own electrical characteristics (for example, resistance value) change in response to a specific gas (measurement gas). The material of the sensitive film 40 may be appropriately selected depending on the gas to be detected, and is not particularly limited. For example, an oxide semiconductor film can be used. Examples of oxide semiconductor films include ZnO, SnO ２ , W.O. ３ , In ２ O ３ , TiO ２ , and V ２ O ５ In the gas sensor 100, when a specific gas reacts with the sensitive film 40 and the resistance value of the sensitive film 40 changes, the current value of the ammeter 3 connected to the power source 2 in the gas sensor device 1 changes. This enables the gas sensor device 1 to detect the specific gas.

[0031] The manufacturing method of the gas sensor 100 is not particularly limited. For example, in the process of forming the laminate 11, as shown in FIG. 2, ion etching may be performed from the surface side of the fifth insulating layers 25L and 25R to form the inclined surfaces 11C, 11E, etc. and the first horizontal surface 11B.

[0032] The gas sensor 100 of this embodiment includes a laminate 11 in which electrode layers 31, 32L and insulating layers 24L are alternately stacked, and a sensitive film 40 that reacts to a measurement gas, in which a recess 11A1 recessed in the stacking direction is formed in the laminate 11, and the recess 11A1 has a side surface 11C that includes end faces of the electrode layers 31, 32L and the insulating layer 24L, and the sensitive film 40 is in contact with one insulating layer 24L and at least one pair of electrode layers 31, 32L that sandwich the insulating layer 24L on the side surface 11C of the recess 11A1.

[0033] In the gas sensor 100, the pair of electrode layers 31, 32L are insulated by the single insulating layer 24R, and the sensitive film 40 is in contact with the pair of electrode layers 31, 32L, so that the gas to be measured reacts with the sensitive film 40, causing, for example, a change in the electrical properties of the sensitive film 40, thereby enabling the gas to be detected with high sensitivity and selectivity through the two electrode layers 31, 32L. Furthermore, because the sensitive film 40 is in contact with the single insulating layer 24L and at least the pair of electrode layers 31, 32L sandwiching it on the side surface 11C of the recess 11A1, this increases the contact area with the sensitive film 40 and provides an anchor effect, thereby enabling the gas sensor 100 to have improved detection sensitivity. For example, if multiple electrode layers 31, 32L are disposed on the surface of the insulating layer 24R and the sensitive membrane 40 is in contact with these electrode layers, unevenness may occur in the sensitive membrane 40 to conform to the shapes of the electrode layers 31, 32L, etc., and discontinuities may occur in these uneven portions. However, in the gas sensor 100 described above, the sensitive membrane 40 is in contact with the pair of electrode layers 31, 32L and the side surface 11C of the recess 11A1, which includes the end faces of the electrode layers 31, 32L and the end face of the insulating layer 24R. This prevents the above-described unevenness from occurring in the sensitive membrane 40. This prevents discontinuities.

[0034] A side surface 11C of the recess 11A1 is inclined with respect to the stacking direction.

[0035] In the gas sensor 100, the contact area with the sensitive film 40 can be increased compared to when the side surfaces of the recesses 11A1 are not inclined but extend in the stacking direction (when the side surfaces of the recesses are perpendicular to the surfaces of the electrode layers), thereby improving detection sensitivity. Furthermore, the sensitive film 40 that contacts the side surfaces 11C of the recesses 11A1 and the electrode layers 31 and 32L can be prevented from being bent at a right angle. This can suppress step disconnection.

[0036] The recess 11A1 has a bottom surface 11B formed by a surface perpendicular to the stacking direction of the electrode layer 31, and the sensitive film 40 is in contact with the bottom surface 11B of the recess 11A1.

[0037] According to the gas sensor 100, the contact area between the electrode layers 31, 32L and the sensitive film 40 can be increased, thereby improving the detection sensitivity.

[0038] The recess 11A1 has an outer shape of a regular hexagon in plan view.

[0039] In the gas sensor 100, the side surfaces 11C of the recess 11A1 that form the regular hexagonal shape of the recess 11A1 in plan view have equal contact distances (areas) with the sensitive film 40. This makes it easier for current to flow evenly along these sides.

[0040] The recesses 11A1 are arranged in a close-packed manner in plan view.

[0041] In the gas sensor 100, when electricity is applied to the electrode layers 31, 32L, current flows uniformly through the recesses 11A1. Furthermore, since the recesses 11A1 are arranged alternately in rows, the recesses 11A1 can be suitably arranged in one gas sensor 100, thereby increasing the contact area with the sensitive membrane 40.

[0042] Second Embodiment Next, a second embodiment of the present disclosure will be described with reference to Fig. 5 etc. In this embodiment, the same components as those in the above embodiment are designated by the same reference numerals, and redundant descriptions of the structure, operation and effects will be omitted.

[0043] 5, the gas sensor 200 includes a first wiring 215 and a second wiring 216 connected to the laminate 211. The first wiring 215 branches into a rear wiring 215A and a front wiring 215B. Similarly, the second wiring 216 branches into a rear wiring 216A and a front wiring 216B. The gas sensor 200, together with the power source 2 and the ammeter 3, constitutes a gas sensor device 201.

[0044] 6 , the laminate 211 includes a plurality of electrode layers 31, 32L and 32R, 233L and 233R, 234L and 234R, and a plurality of insulating layers 21, 22, 23, 24L and 24R, 25L and 25R, 226L and 226R, and 227L and 227R stacked in the stacking direction (vertical direction). On the surface of the left-side fifth insulating layer 25L, a left-side third electrode layer 233L, a left-side sixth insulating layer 226L, a left-side fourth electrode layer 234L, and a left-side seventh insulating layer 227L are stacked in this order. On the surface of the right-side fifth insulating layer 25R, a right-side third electrode layer 233R, a right-side sixth insulating layer 226R, a right-side fourth electrode layer 234R, and a right-side seventh insulating layer 227R are stacked in this order.

[0045] 1 is connected to the first electrode layer 31. A rear wiring 215A of the first wiring 215 shown in FIG. 1 is connected to the second electrode layers 32L and 32R. A front wiring 215B of the first wiring 215 is connected to the third electrode layers 233L and 233R. A front wiring 216B of the second wiring 216 is connected to the fourth electrode layers 234L and 234R.

[0046] In the surface 211A of the laminate 211, the first horizontal surface 11B is the surface (top surface) of the thin layer portion 36. One inclined surface 211C is a surface formed by connecting the side surfaces of the gradually changing layer portion 37L, the fourth insulating layer 24L, the second electrode layer 32L, the fifth insulating layer 25L, the third electrode layer 233L, the sixth insulating layer 226L, the fourth electrode layer 234L, and the seventh insulating layer 227L. The other inclined surface 211E has a configuration similar to (bilaterally symmetrical with) the one inclined surface 211C. The first horizontal surface 11B and the inclined surfaces 211C and 211E form a recess 211A1 recessed in the stacking direction from the second horizontal surfaces 211D and 211F in the laminate 211. The second horizontal surfaces 211D and 211F are surfaces (upper surfaces) of the seventh insulating layers 227L and 227R, respectively. The sensitive film 240 contacts the first horizontal surface 211B and the inclined surfaces 211C and 211E, and further contacts each of the inclined surfaces 211C and 211E and each of the second horizontal surfaces 211D and 211F.

[0047] Third Embodiment Next, a third embodiment of the present disclosure will be described with reference to Fig. 7. In this embodiment, the surface shape of the laminate 11 of the first embodiment is changed, and the parts corresponding to those of the first embodiment are designated by reference numerals in which the tens digit of the numeral portion is changed from 1 to 5, and redundant explanations of the structure, action, and effect will be omitted.

[0048] 7, the surface 51A of the laminate 51 includes a first horizontal surface 51B extending perpendicularly (horizontally) to the stacking direction, a second horizontal surface 51D disposed above the first horizontal surface 51B, and an inclined surface 51C inclined with respect to the stacking direction. The inclined surface 51C and the second horizontal surface 51B form a bottomed recess 5D. The recess 5D has a circular outer shape in a plan view.

[0049] Fourth Embodiment Next, a fourth embodiment of the present disclosure will be described with reference to Fig. 8. In this embodiment, the surface shape of the laminate 11 of the first embodiment is changed, and parts corresponding to those of the first embodiment are designated by reference numerals in which the tens digit of the numeral portion is changed from 1 to 6, and redundant explanations of the structure, action, and effect will be omitted.

[0050] 8, the surface 61A of the laminate 61 includes a first horizontal surface 61B extending perpendicularly (horizontally) to the stacking direction, a second horizontal surface 61D disposed above the first horizontal surface 61B, and an inclined surface 61C inclined with respect to the stacking direction. The inclined surface 61C and the second horizontal surface 61B form a bottomed recess 6D. The outer shape of the recess 6D is an equilateral triangle in plan view.

[0051] Fifth Embodiment Next, a fifth embodiment of the present disclosure will be described with reference to Fig. 9. In this embodiment, the surface shape of the laminate 11 of the first embodiment is changed, and parts corresponding to those of the first embodiment are designated by reference numerals in which the tens digit of the numeral portion is changed from 1 to 7, and redundant explanations of the structure, action, and effect will be omitted.

[0052] 9 , the surface 71A of the laminate 71 includes a first horizontal surface 71B extending perpendicularly (horizontally) to the stacking direction, a second horizontal surface 71D disposed above the first horizontal surface 71B, and an inclined surface 71C inclined with respect to the stacking direction. The inclined surface 71C and the second horizontal surface 71B form a bottomed recess 7D. The recess 7D has a diamond-shaped outer shape in a plan view.

[0053] <Other Embodiments> The present disclosure is not limited to the embodiments described above and in the drawings. For example, the following embodiments are also included within the technical scope of the present disclosure. Furthermore, various modifications other than those described below can be made without departing from the spirit of the present disclosure.

[0054] (1) In addition to the above-described embodiments, the configuration of the laminate can be modified as appropriate. The laminate may be configured to include at least a first electrode layer, an insulating layer laminated on the first electrode layer, and a second electrode layer laminated on the insulating layer. In such a configuration, the top surface of the second electrode layer may be in contact with the sensitive membrane.

[0055] (2) In addition to the above-described embodiment, the configuration of the sensitive film can be modified as appropriate. The sensitive film may be in contact with the first horizontal surface and the inclined surface, but not the second horizontal surface. Alternatively, the sensitive film may be in contact with a portion of the first horizontal surface and an inclined surface that is continuous with the portion of the first horizontal surface.

[0056] (3) The configuration of the recesses can be changed as appropriate. The side surfaces (inclined surfaces) of the recesses may extend in a direction parallel to the stacking direction. The planar shape of the recesses is not limited to a regular hexagon, equilateral triangle, rhombus, or circle, but may also be other triangles, rectangles, or other polygons. Furthermore, on the surface of the laminate, multiple recesses with an outer shape extending in one direction may be arranged in a slit-like configuration in plan view.

[0057] (4) The wiring configuration can be changed as appropriate. In the above embodiment, the wiring is arranged so as to connect to both sides of the stack (both the left and right sides of the paper in FIG. 1 ), but this is not limited thereto. For example, the wiring may be arranged so as to connect to the front side of the stack (the lower side of the paper in FIG. 1 ).

[0058] (5) In the gas sensor device, the instrument for measuring the electrical characteristics is not limited to an ammeter that measures current, but may be a measuring instrument that measures various electrical characteristics, such as a voltmeter or an ohmmeter.

[0059] 11, 211... laminated body, 11A1, 211A1... recessed portion, 11B... first horizontal surface (bottom surface), 11C, 11E, 211C, 211E... inclined surface (side surface), 24L, 24R, 224L, 224R... fourth insulating layer (single insulating layer), 31... first electrode layer, 32L, 32R... second electrode layer, 40, 240... sensitive film, 100, 200... gas sensor

Claims

1. A gas sensor comprising a laminate in which electrode layers and insulating layers are alternately stacked, and a sensitive film that reacts to a gas to be measured, wherein the laminate has a recess that is recessed in the stacking direction, the recess has side surfaces that include an end face of the electrode layer and an end face of the insulating layer, and the sensitive film is in contact with one insulating layer and at least a pair of electrode layers that sandwich it on the side surfaces of the recess.

2. The gas sensor according to claim 1, wherein a side surface of the recess is inclined with respect to the stacking direction.

3. A gas sensor according to claim 1 or 2, wherein the recess has a bottom surface constituted by a surface perpendicular to the stacking direction of the electrode layers, and the sensitive film is in contact with the bottom surface of the recess.

4. The gas sensor according to claim 1 or 2, wherein the outer shape of the recess is a regular hexagon, a circle, an equilateral triangle, or a rhombus in a plan view.

5. The gas sensor according to claim 1 or 2, wherein the recesses are arranged in a close-packed manner in a plan view.

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