Patent Publication Number: US-2022238275-A1

Title: Composite capacitor

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     The present application is a continuation of International application No. PCT/JP2020/026831, filed Jul. 9, 2020, which claims priority to Japanese Patent Application No. 2019-193614, filed Oct. 24, 2019, the entire contents of each of which are incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to a composite capacitor. 
     BACKGROUND OF THE INVENTION 
     An example of a document that discloses a capacitor including columnar conductors each having a nano-size outer diameter is Japanese Patent No. 5511746 (Patent Document 1). In the capacitor disclosed in Patent Document 1, carbon nanotubes are oriented to extend upward in the substantially vertical direction from a catalyst pad. A dielectric layer is deposited on the catalyst pad. The dielectric layer also covers the outer side portion of each of the carbon nanotubes. A blanket layer made of a conductive material deposited on an insulating substrate fills space between the adjacent carbon nanotubes and also covers the nanotubes, the insulating substrate, and the catalyst pad. 
     SUMMARY OF THE INVENTION 
     To increase the electrostatic capacity of the capacitor disclosed in Patent Document 1, the capacitor may be enlarged in the arranging direction of the carbon nanotubes, which serve as the columnar conductors. However, if the electrostatic capacity is increased in this manner, the capacitance density per unit area as viewed from the extending direction of the columnar conductors is not enhanced. 
     Additionally, in the capacitor disclosed in Patent Document 1, counter electrodes are arranged in the top-down direction. When a plurality of such capacitors are prepared and are stacked on each other, they are connected in series with each other. In a composite capacitor configured as described above, the overall electrostatic capacity is not increased. 
     The present invention has been made in view of the above-described problems. It is an object of the invention to provide a composite capacitor which can enhance the capacitance density per unit area as viewed from the stacking direction of capacitors and which can also increase the electrostatic capacity. 
     A composite capacitor according to the present invention includes a plurality of capacitors stacked on each other; and an insulating section that covers peripheral surfaces of the plurality of capacitors about a central axis of the plurality of capacitors, a stacking direction of the plurality of capacitors being a direction of the central axis. Each of the plurality of capacitors includes: a support electrode layer; a plurality of columnar conductors that extend from a side of the support electrode layer along the stacking direction and that each have a nano-size outer diameter; a dielectric layer that covers the support electrode layer and the plurality of columnar conductors; and a counter electrode layer that covers the dielectric layer and that opposes the support electrode layer and the plurality of columnar conductors with the dielectric layer interposed therebetween. The plurality of capacitors include a first capacitor and a second capacitor connected in parallel with the first capacitor. 
     According to the present invention, in a composite capacitor, the capacitance density per unit area as viewed from the stacking direction of capacitors can be enhanced, and the electrostatic capacity can also be increased. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a sectional view of a composite capacitor according to a first embodiment of the invention. 
         FIG. 2  is a sectional view of a composite capacitor according to a modified example of the first embodiment of the invention. 
         FIG. 3  is a sectional view of a composite capacitor according to a comparative example. 
         FIG. 4  is a sectional view illustrating a state in which plural columnar conductors are formed on a substrate in a manufacturing method for the composite capacitor according to the first embodiment of the invention. 
         FIG. 5  is a sectional view illustrating a state in which the plural columnar conductors are transferred from the substrate to a collective support electrode layer in the manufacturing method for the composite capacitor according to the first embodiment of the invention. 
         FIG. 6  is a sectional view illustrating a state in which the collective support electrode layer and the plural columnar conductors are coated with a dielectric layer in the manufacturing method for the composite capacitor according to the first embodiment of the invention. 
         FIG. 7  is a sectional view illustrating a state in which the dielectric layer is coated with a counter electrode layer in the manufacturing method for the composite capacitor according to the first embodiment of the invention. 
         FIG. 8  is a sectional view illustrating a state in which the counter electrode layer is flattened in the manufacturing method for the composite capacitor according to the first embodiment of the invention. 
         FIG. 9  is a sectional view illustrating a state in which the counter electrode layer is divided in the manufacturing method for the composite capacitor according to the first embodiment of the invention. 
         FIG. 10  is a sectional view illustrating a state in which each of the collective support electrode layer and the dielectric layer is divided in the manufacturing method for the composite capacitor according to the first embodiment of the invention. 
         FIG. 11  is a sectional view illustrating a state in which an insulating section is provided for each of the plural capacitors in the manufacturing method for the composite capacitor according to the first embodiment of the invention. 
         FIG. 12  is a sectional view of a composite capacitor according to a second embodiment of the invention. 
         FIG. 13  is a sectional view of a composite capacitor according to a third embodiment of the invention. 
         FIG. 14  is a sectional view of a composite capacitor according to a fourth embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Hereinafter, composite capacitors according to individual embodiments of the present invention will be described below with reference to the drawings. In the following description of the embodiments, identical or corresponding elements will be designated by like reference numeral and an explanation thereof will not be repeated. 
     First Embodiment 
       FIG. 1  is a sectional view of a composite capacitor according to a first embodiment of the invention. As shown in  FIG. 1 , a composite capacitor  1  according to the first embodiment of the invention includes plural capacitors  10  and an insulating section  20 . The plural capacitors  10  are stacked on each other. The insulating section  20  covers peripheral surfaces  11  of the plural capacitors  10  about the central axis of the plural capacitors  10 , assuming that the stacking direction of the plural capacitors  10  is the direction of the central axis. 
     The configurations of all the plural capacitors  10  are the same and will first be discussed below. As shown in  FIG. 1 , the plural capacitors  10  each include a support electrode layer  100 , plural columnar conductors  110 , a dielectric layer  120 , and a counter electrode layer  130 . 
     The support electrode layer  100  may be formed in the shape of a plane, foil, or thin film. The support electrode layer  100  formed in a planar shape is easy to handle during the manufacturing of the composite capacitor  1  and the composite capacitor  1  is thus easy to design. The support electrode layer  100  formed in a foil-like shape is easy to handle during the manufacturing of the composite capacitor  1 . The support electrode layer  100  formed in a thin-film-like shape can lower the height of the composite capacitor  1 . 
     The external shape and the area of the support electrode layer  100  as viewed from the stacking direction of the plural capacitors  10  can suitably be designed in terms of the electrostatic capacity of the capacitors  10 . The external shape of the support electrode layer  100  is a rectangle, a rectangle having curved corners, or an ellipse, as viewed from the above-described stacking direction. A hole may be formed in the support electrode layer  100 , as viewed from the above-described stacking direction. 
     The material forming the support electrode layer  100  is not limited to a particular type. The support electrode layer  100  may be made of a metal, such as copper. If the support electrode layer  100  is made of a metal, a conductive path can be easily formed when the support electrode layer  100  is brought into contact with another conductive member. Additionally, the support electrode layer  100  made of a metal can make its resistance relatively low and also improve its heat resistance. 
     The support electrode layer  100  may include wiring, which is used for forming a conductive path by connecting the support electrode layer  100  to another conductive member such as the plural columnar conductors  110 . If the support electrode layer  100  includes wiring, the portion of the support electrode layer  100  other than the wiring may be formed of an insulating material, such as a ceramic material. If the portion of the support electrode layer  100  other than the wiring is formed of a ceramic material, the mechanical characteristics of the support electrode layer  100  are enhanced. 
     The plural columnar conductors  110  are each supported by the support electrode layer  100 . At one side of the support electrode layer  100  in the stacking direction, each of the plural columnar conductors  110  extends from the support electrode layer  100  along the stacking direction. Although in this embodiment each of the plural columnar conductors  110  extends from the surface of the support electrode layer  100 , it may extend outwardly from the inside of the support electrode layer  100 . Additionally, although in this embodiment each of the plural columnar conductors  110  is formed of a member different from the support electrode layer  100 , it may be formed of a uniform member together with the support electrode layer  100 . 
     Each of the plural columnar conductors  110  has a nano-size outer diameter. In the present specification, the nano size is 0.1 nm to 1000 nm, for example. Each of the plural columnar conductors  110  may have a cylindrical shape or a cylindrical shape with a closed bottom. 
     The material forming the plural columnar conductors  110  is not limited to a particular type. In this embodiment, the plural columnar conductors  110  are made of a conductive material or a semiconductor material. However, the plural columnar conductors  110  may be formed of columnar members made of a semiconductor material or insulating material thinly coated with a metal. 
     Each of the plural columnar conductors  110  includes, for example, carbon nanofibers, another type of nanofibers made of ZnO, for example, or nanorods or nanowires made of ZnO, GaN, or hematite. In this embodiment, specifically, the plural columnar conductors  110  are formed of carbon nanotubes, and more specifically, each of the plural columnar conductors  110  is formed of multiple, for example, 100 to 200, carbon nanotubes. 
     In this embodiment, the chirality of the carbon nanotubes is not limited to a particular type. The carbon nanotubes may be of a semiconductor type or a metal type. The carbon nanotubes may include both of nanotubes of a semiconductor type and those of a metal type. From the viewpoint of the electrical resistance, the carbon nanotubes preferably have a higher ratio of nanotubes of a metal type than those of a semiconductor type. 
     In this embodiment, the number of layers forming the carbon nanotubes is not particularly restricted. The carbon nanotubes may be of a SWCNT (Single Wall Carbon Nanotube) type formed of one layer or of a MWCNT (Multiwall Carbon Nanotube) type formed of two or more layers. 
     The length of each of the plural columnar conductors  110  is not particularly limited. The length of each of the plural columnar conductors  110  is preferably long from the viewpoint of the capacitance density per unit area in the planar direction perpendicular to the extending direction of the plural columnar conductors  110 . The length of each of the plural columnar conductors  110  is several micrometers or longer, 20 μm or longer, 50 μm or longer, 100 μm or longer, 500 μm or longer, 750 μm or longer, 1000 μm or longer, or 2000 μm or longer, for example. 
     The lengths of the plural columnar conductors  110  may be different from each other. The forward ends of the plural columnar conductors  110  are preferably aligned on a virtual plane substantially perpendicular to the stacking direction. This configuration can easily control the electrostatic capacity of the capacitor  10 . 
     At the above-described side of the support electrode layer  100  in the stacking direction, the dielectric layer  120  covers the support electrode layer  100  and the plural columnar conductors  110 . The dielectric layer  120  covers the entire surface of the support electrode layer  100  on the side of the plural columnar conductors  110 , except for the portions on which the plural columnar conductors  110  are disposed. 
     An additional conductor layer may be disposed between the dielectric layer  120  and the plural columnar conductors  110 . This can further reduce the parasitic resistance of the capacitor  10 . 
     The material forming the dielectric layer  120  is not limited to a particular type. Examples of the material are silicon dioxide, aluminum oxide, silicon nitride, tantalum oxide, hafnium oxide, barium titanate, lead zirconate titanate, and a combination thereof. 
     The counter electrode layer  130  covers the dielectric layer  120  and opposes the support electrode layer  100  and the plural columnar conductors  110  with the dielectric layer  120  interposed therebetween. In this embodiment, a surface of the counter electrode layer  130 , which is the opposite side of the counter electrode layer  130  as viewed from the support electrode layer  100 , has a planar shape. 
     The material forming the counter electrode layer  130  is not limited to a particular type, and may be a metal, such as silver, gold, copper, platinum, aluminum, or an alloy thereof. 
     The overall configuration of the composite capacitor  1  will now be discussed below. 
     In the composite capacitor  1  according to the present embodiment, the plural capacitors  10  include a first capacitor  10 A, a second capacitor  10 B, and a third capacitor  10 C. 
     The second capacitor  10 B is located on one side of the first capacitor  10 A, which is one side in the stacking direction of the plural capacitors  10  and which is the extending side of the plural columnar conductors  110 . In this embodiment, the counter electrode layer  130  of the first capacitor  10 A, which is one of the plural capacitors  10 , is electrically connected directly to the support electrode layer  100  of the second capacitor  10 B, which is another capacitor  10  positioned most closely to the first capacitor  10 A at the side of the counter electrode layer  130  of the first capacitor  10 A in the stacking direction. The counter electrode layer  130  of the first capacitor  10 A and the support electrode layer  100  of the second capacitor  10 B are bonded to each other only with a conductive adhesive  30  interposed therebetween. 
     The third capacitor  10 C is located on one side of the second capacitor  10 B, which is one side in the stacking direction of the plural capacitors  10  and which is the extending side of the plural columnar conductors  110 . In this embodiment, the counter electrode layer  130  of the second capacitor  10 B, which is one of the plural capacitors  10 , is electrically connected directly to the support electrode layer  100  of the third capacitor  10 C, which is another capacitor  10  positioned most closely to the second capacitor  10 B at the above-described side of the counter electrode layer  130  of the second capacitor  10 B in the stacking direction. The counter electrode layer  130  of the second capacitor  10 B and the support electrode layer  100  of the third capacitor  10 C are bonded to each other only with a conductive adhesive  30  interposed therebetween. 
     The support electrode layer  100  of the first capacitor  10 A, which is one of the plural capacitors  10 , and the dielectric layer  120  covering this support electrode layer  100  extend to cut out an end portion of the insulating section  20  and further extend to the opposite side of the insulating section  20  as viewed from the capacitor  10 . 
     The support electrode layer  100  of the second capacitor  10 B, which is one of the plural capacitors  10 , and the dielectric layer  120  covering this support electrode layer  100  pass through the insulating section  20  and extend to the opposite side of the insulating section  20  as viewed from the capacitor  10 . In this embodiment, the extending direction of the support electrode layer  100  and the dielectric layer  120  of the second capacitor  10 B is different from that of the support electrode layer  100  and the dielectric layer  120  of the first capacitor  10 A. 
     The support electrode layer  100  of the third capacitor  10 C, which is one of the plural capacitors  10 , and the dielectric layer  120  covering this support electrode layer  100  pass through the insulating section  20  and extend to the opposite side of the insulating section  20  as viewed from the capacitor  10 . In this embodiment, the extending direction of the support electrode layer  100  and the dielectric layer  120  of the third capacitor  10 C is substantially the same as that of the support electrode layer  100  and the dielectric layer  120  of the first capacitor  10 A. 
     The composite capacitor  1  according to the present embodiment further includes a top-surface electrode layer  40 . The configuration of the top-surface electrode layer  40  is similar to that of the support electrode layer  100 . The top-surface electrode layer  40  is electrically connected directly to the counter electrode layer  130  of the third capacitor  10 C, which is the capacitor  10  positioned farther toward the above-described side in the stacking direction than the other capacitors  10 . The top-surface electrode layer  40  is located at the opposite side of the counter electrode layer  130  as viewed from the support electrode layer  100 . The counter electrode layer  130  of the third capacitor  10 C and the top-surface electrode layer  40  are bonded to each other only with a conductive adhesive  30  interposed therebetween. 
     The top-surface electrode layer  40  extends to cut out an end portion of the insulating section  20  and further extends to the opposite side of the insulating section  20  as viewed from the capacitor  10 . In this embodiment, the extending direction of the top-surface electrode layer  40  is substantially the same as that of the support electrode layer  100  and the dielectric layer  120  of the second capacitor  10 B. 
     It may be possible that the composite capacitor  1  according to the first embodiment of the invention does not include the top-surface electrode layer  40 .  FIG. 2  is a sectional view of a composite capacitor according to a modified example of the first embodiment of the invention. As shown in  FIG. 2 , a composite capacitor  1   a  according to the modified example of the first embodiment of the invention does not include a top-surface electrode layer. In the composite capacitor  1   a  of this modified example, the counter electrode layer  130  of the third capacitor  10 C is exposed to the exterior. 
     The circuit constituted by the three capacitors  10  included in the composite capacitor  1  according to the first embodiment of the invention will be explained below upon comparison with a composite capacitor according to a comparative example. 
       FIG. 3  is a sectional view of a composite capacitor according to the comparative example. As shown in  FIG. 3 , a composite capacitor  9  according to the comparative example is different from the composite capacitor  1  according to the first embodiment of the invention in that the support electrode layers  100 , the dielectric layers  120 , and the top-surface electrode layer  40  do not extend to opposite sides of the insulating section  20  as viewed from the capacitors  10 . 
     In the composite capacitor  9  according to the comparative example, if the support electrode layer  100  of the first capacitor  10 A is used as one terminal and the top-surface electrode layer  40  is used as the other terminal, a circuit is formed from one terminal to the other terminal. In this circuit, the plural capacitors  10  are connected in series with each other. That is, in the composite capacitor  9  according to the comparative example, the first capacitor  10 A, the second capacitor  10 B, and the third capacitor  10 C are not connected in parallel with each other. 
     In contrast, in the composite capacitor  1  according to the first embodiment of the invention, as shown in  FIG. 1 , the support electrode layer  100  of the first capacitor  10 A and that of the third capacitor  10 C are electrically connected to each other so as to be used as one terminal. The support electrode layer  100  of the second capacitor  10 B and the top-surface electrode layer  40  are electrically connected to each other so as to be used as the other terminal. 
     In the circuit formed from one terminal to the other terminal of the composite capacitor  1  of this embodiment, the second capacitor  10 B is connected in parallel with the first capacitor  10 A, while the third capacitor  10 C is connected in parallel with each of the first capacitor  10 A and the second capacitor  10 B. In this manner, in the composite capacitor  1  according to the present embodiment, the three capacitors  10  can be represented by three parallel-connection arrangements×one series-connection arrangement. 
     Hereinafter, the manufacturing method for the composite capacitor  1  according to the first embodiment of the invention will be described below. The manufacturing method for the composite capacitor  1  is not restricted to a particular method. The manufacturing method for the composite capacitor  1  according to the first embodiment of the invention includes a step of forming columnar conductors on a substrate, a step of transferring the columnar conductors to a collective support electrode layer, a step of applying a dielectric layer, a step of applying a counter electrode layer, a step of flattening the counter electrode layer, a step of dividing the counter electrode layer, a step of dividing each of the collective support electrode layer and the dielectric layer, a step of providing an insulating section, and a stacking step. 
       FIG. 4  is a sectional view illustrating a state in which plural columnar conductors are formed on a substrate in the manufacturing method for the composite capacitor according to the first embodiment of the invention. As shown in  FIG. 4 , plural columnar conductors  110  are first formed on a substrate  200 . More specifically, catalyst particles are disposed on the substrate  200  and the columnar conductors  110  are grown from the catalyst particles. The plural columnar conductors  110  each have an end portion  115  at the opposite side of the columnar conductor  110  as viewed from the substrate  200 . 
     If the columnar conductors  110  are carbon nanotubes, the catalyst particles are made of Fe, Ni, Co, or an alloy thereof, for example. If the columnar conductors  110  contain ZnO, the catalyst particles are made of Pt, Au, or an alloy thereof. To dispose the catalyst particles, a combination of one of CVD (Chemical Vapor Deposition), sputtering, and PVD (Physical Vapor Deposition) and one of lithography and etching may be used. The position of the catalyst particles is suitably selected by patterning. 
     The process for growing the columnar conductors  110  is not restricted to a particular process. In this embodiment, the plural columnar conductors  110  can be grown by CVD or plasma-enhanced CVD, for example. A gas used in CVD or plasma-enhanced CVD may be carbon monoxide, methane, ethylene, acetylene, or a mixture of such a compound and hydrogen or ammonia. 
     Each of the plural columnar conductors  110  is grown from the surface of the catalyst particles. Each of the plural columnar conductors  110  is grown such that the end portion  115  is separated from the substrate  200 . 
     When the plural columnar conductors  110  are grown with the above-described CVD or plasma-enhanced CVD, for example, if conditions such as the temperature condition and the gas condition are suitably selected, each of the plural columnar conductors  110  can be formed to have a length within a desired range and an outer diameter within a desired range. The specific lengths of the plural columnar conductors  110  become different from each other depending on the gas concentration, gas flow rate, and temperature variations on the surface of the substrate  200 . 
     Examples of the material forming the substrate  200  are silicon oxide, silicon, gallium arsenide, aluminum, and SUS. 
       FIG. 5  is a sectional view illustrating a state in which the plural columnar conductors are transferred from the substrate to a collective support electrode layer in the manufacturing method for the composite capacitor according to the first embodiment of the invention. As shown in  FIG. 5 , the plural columnar conductors  110  formed on the substrate  200  are bonded at their end portions  115  onto a collective support electrode layer  100 X. After the plural columnar conductors  110  are bonded to the collective support electrode layer  100 X, the substrate  200  is removed from the plural columnar conductors  110 . In this manner, the plural columnar conductors  110  are transferred from the substrate  200  to the collective support electrode layer  100 X. The collective support electrode layer  100 X is a collective body of the support electrode layers  100  of the plural capacitors  10 . More specifically, the collective support electrode layer  100 X is in a state in which the plural support electrode layers  100  are connected with each other in the in-plane direction. 
     The plural columnar conductors  110  may be transferred from the substrate  200  to the collective support electrode layer  100 X by chemically or mechanically inserting the plural columnar conductors  110  into the collective support electrode layer  100 X. With this approach, the lengths of the plural columnar conductors  110  extending from the support electrode layer  100  to the exterior can be made uniform. 
     If each of the plural columnar conductors  110  is formed of a uniform member together with the support electrode layer  100 , instead of the above-described process, one planar electrode layer may be used and the surface of the planar electrode layer may be processed in an uneven form by chemical etching, for example, thereby forming the plural columnar conductors  110  and the collective support electrode layer  100 X. 
       FIG. 6  is a sectional view illustrating a state in which the collective support electrode layer and the plural columnar conductors are coated with a dielectric layer in the manufacturing method for the composite capacitor according to the first embodiment of the invention. As shown in  FIG. 6 , the dielectric layer  120  is applied to the entire surface of the collective support electrode layer  100 X on which the plural columnar conductors  110  are disposed. The process for applying the dielectric layer  120  is not restricted to a particular process, and plating, ALD (Atomic Layer Deposition), CVD, MOCVD (Metalorganic Chemical Vapor Deposition), supercritical fluid film deposition, or sputtering, for example, may be used. 
       FIG. 7  is a sectional view illustrating a state in which the dielectric layer is coated with a counter electrode layer in the manufacturing method for the composite capacitor according to the first embodiment of the invention. As shown in  FIG. 7 , the counter electrode layer  130  is applied onto the dielectric layer  120 . The process for applying the counter electrode layer  130  is not restricted to a particular process, and plating, ALD, CVD, MOCVD, supercritical fluid film deposition, or sputtering, for example, may be used. 
       FIG. 8  is a sectional view illustrating a state in which the counter electrode layer is flattened in the manufacturing method for the composite capacitor according to the first embodiment of the invention. As shown in  FIG. 8 , a portion of the counter electrode layer  130 , which is the opposite side of the counter electrode layer  130  as viewed from the collective support electrode layer  100 X on which the plural columnar conductors  110  are formed, is flattened by CMP (Chemical Mechanical Polishing). 
       FIG. 9  is a sectional view illustrating a state in which the counter electrode layer is divided in the manufacturing method for the composite capacitor according to the first embodiment of the invention. As shown in  FIG. 9 , the plural columnar conductors  110  are split into multiple groups, and the counter electrode layer  130  is divided into multiple counter electrode layers  130  so that the divided counter electrode layers  130  are separated from each other in accordance with the multiple groups of the plural columnar conductors  110 . The dielectric layer  120  positioned between the plural counter electrode layers  130  is exposed. Dividing of the counter electrode layer  130  is performed by photomasking and etching. 
       FIG. 10  is a sectional view illustrating a state in which each of the collective support electrode layer and the dielectric layer is divided in the manufacturing method for the composite capacitor according to the first embodiment of the invention. As shown in  FIG. 10 , at positions at which the dielectric layer  120  is exposed, the collective support electrode layer  100 X and the dielectric layer  120  are cut with a dicing machine and divided. This can form the plural capacitors  10  in association with the plural support electrode layers  100  formed by dividing the collective support electrode layer  100 X. The collective support electrode layer  100 X and the dielectric layer  120  are divided so that each support electrode layer  100  and each dielectric layer  120  extend in one direction of the capacitors  10 . 
       FIG. 11  is a sectional view illustrating a state in which an insulating section is provided for each of the plural capacitors in the manufacturing method for the composite capacitor according to the first embodiment of the invention. As shown in  FIG. 11 , the insulating section  20  is disposed on the peripheral surface  11  of each of the plural capacitors  10 . The process for providing the insulating section  20  is not restricted to a particular process, and plating, ALD, CVD, MOCVD, supercritical fluid film deposition, or sputtering, for example, may be used. Alternatively, the insulating section  20  may be provided by applying a paste base including an insulating material to the peripheral surface  11  of each capacitor  10  and then by firing the paste base. 
     Lastly, the plural capacitors  10  provided with the insulating section  20  and the top-surface electrode layer  40  are stacked on each other with a conductive adhesive  30  interposed between. As a result, the composite capacitor according to the first embodiment of the invention, such as that shown in  FIG. 1 , is manufactured. Before providing the insulating section  20  for each of the plural capacitors  10 , the capacitors  10  may be stacked on each other, and then, the insulating section  20  may be provided for the plural capacitors  10  stacked on each other. In the stacking step, if the plural capacitors  10  provided with the insulating section  20  are merely stacked on each other with a conductive adhesive  30  interposed therebetween, the composite capacitor  1   a  according to the modified example of the first embodiment of the invention is manufactured. 
     As described above, the composite capacitor  1  according to the first embodiment of the invention includes the plural capacitors  10  and the insulating section  20 . The plural capacitors  10  are stacked on each other. The insulating section  20  covers the peripheral surfaces  11  of the plural capacitors  10  about the central axis of the plural capacitors  10 , assuming that the stacking direction of the plural capacitors  10  is the direction of the central axis. Each of the plural capacitors  10  includes the support electrode layer  100 , the plural columnar conductors  110 , the dielectric layer  120 , and the counter electrode layer  130 . At one side of the support electrode layer  100  in the stacking direction, each of the plural columnar conductors  110  extends from the support electrode layer  100  along the stacking direction. Each of the plural columnar conductors  110  has a nano-size outer diameter. At the above-described side of the support electrode layer  100 , the dielectric layer  120  covers the support electrode layer  100  and the plural columnar conductors  110 . The counter electrode layer  130  covers the dielectric layer  120  and opposes the support electrode layer  100  and the plural columnar conductors  110  with the dielectric layer  120  interposed therebetween. The plural capacitors  10  include the first capacitor  10 A and the second capacitor  10 B. The second capacitor  10 B is located at the above-described side of the first capacitor  10 A in the stacking direction. The second capacitor  10 B is connected in parallel with the first capacitor  10 A. 
     With this configuration, the composite capacitor  1  can enhance the capacitance density per unit area as viewed from the stacking direction of the capacitors  10  and also increase the electrostatic capacity. 
     In the composite capacitor  1  according to the present embodiment, the support electrode layer  100  of at least one of the plural capacitors  10  passes through the insulating section  20  and extends to the opposite side of the insulating section  20  as viewed from the capacitor  10 . 
     With this configuration, the extending support electrode layer  100  can be used as a terminal of the composite capacitor  1  so as to connect plural capacitors  10  in parallel with each other. 
     In the composite capacitor  1  according to the present embodiment, the counter electrode layer  130  of at least a certain one of the plural capacitors  10  is electrically connected to the support electrode layer  100  of a different capacitor  10  which is positioned most closely to the above-described certain one of the capacitors  10  at the above-described side of the counter electrode layer  130  in the stacking direction. 
     With this configuration, inside the insulating section  20 , the electrode layers of plural capacitors  10  can be electrically connected to each other. 
     In the composite capacitor  1  according to the present embodiment, the support electrode layer  100  of the above-described different capacitor  10  passes through the insulating section  20  and extends to the opposite side of the insulating section  20  as viewed from the different capacitor  10 . 
     With this configuration, the counter electrode layer  130  of the above-described certain one of the capacitors  10  can be used as a terminal of the composite capacitor  1  via the extending support electrode layer  100  of the above-described different capacitor  10  so as to connect plural capacitors  10  in parallel with each other. 
     In the composite capacitor  1  according to the present embodiment, the plural columnar conductors  110  are formed of carbon nanotubes. 
     This can improve the mechanical characteristics of the plural columnar conductors  110 . Hence, when the plural capacitors  10  are stacked on each other, the structure of the capacitors  10  is less likely to change and the electrostatic capacity of the composite capacitor  1  is less likely to decrease. 
     Second Embodiment 
     Hereinafter, a composite capacitor according to a second embodiment of the invention will be described below. The composite capacitor according to the second embodiment of the invention is different from the composite capacitor  1  according to the first embodiment of the invention mainly in that some of plural capacitors are connected in series with each other. An explanation of elements configured similarly to those of the first embodiment of the invention will not be repeated. 
       FIG. 12  is a sectional view of a composite capacitor according to the second embodiment of the invention. As shown in  FIG. 12 , in a composite capacitor  2  according to the second embodiment of the invention, plural capacitors  10  include a first capacitor  10 A, a second capacitor  10 B, a fourth capacitor  10 D, and a fifth capacitor  10 E. 
     The fourth capacitor  10 D is located on one side of the first capacitor  10 A, which is one side in the stacking direction of the plural capacitors  10  and which is the extending side of the plural columnar conductors  110 . In this embodiment, the counter electrode layer  130  of the first capacitor  10 A, which is one of the plural capacitors  10 , is electrically connected directly to the support electrode layer  100  of the fourth capacitor  10 D, which is another capacitor  10  positioned most closely to the first capacitor  10 A at the side of the counter electrode layer  130  of the first capacitor  10 A in the stacking direction. The counter electrode layer  130  of the first capacitor  10 A and the support electrode layer  100  of the fourth capacitor  10 D are bonded to each other only with a conductive adhesive  30  interposed therebetween. 
     The second capacitor  10 B is located on one side of the fourth capacitor  10 D, which is one side in the stacking direction of the plural capacitors  10  and which is the extending side of the plural columnar conductors  110 . In this embodiment, the counter electrode layer  130  of the fourth capacitor  10 D, which is one of the plural capacitors  10 , is electrically connected directly to the support electrode layer  100  of the second capacitor  10 B, which is another capacitor  10  positioned most closely to the fourth capacitor  10 D at the side of the counter electrode layer  130  of the fourth capacitor  10 D in the stacking direction. The counter electrode layer  130  of the fourth capacitor  10 D and the support electrode layer  100  of the second capacitor  10 B are bonded to each other only with a conductive adhesive  30  interposed therebetween. 
     That is, in this embodiment, the counter electrode layer  130  of the first capacitor  10 A and the support electrode layer  100  of the second capacitor  10 B are electrically connected indirectly to each other via the fourth capacitor  10 D. 
     The fifth capacitor  10 E is located on one side of the second capacitor  10 B, which is one side in the stacking direction of the plural capacitors  10  and which is the extending side of the plural columnar conductors  110 . In this embodiment, the counter electrode layer  130  of the second capacitor  10 B, which is one of the plural capacitors  10 , is electrically connected directly to the support electrode layer  100  of the fifth capacitor  10 E, which is another capacitor  10  positioned most closely to the second capacitor  10 B at the side of the counter electrode layer  130  of the second capacitor  10 B in the stacking direction. The counter electrode layer  130  of the second capacitor  10 B and the support electrode layer  100  of the fifth capacitor  10 E are bonded to each other only with a conductive adhesive  30  interposed therebetween. 
     The support electrode layer  100  of the fourth capacitor  10 D and the dielectric layer  120  covering this support electrode layer  100  and the support electrode layer  100  of the fifth capacitor  10 E and the dielectric layer  120  covering this support electrode layer  100  do not pass through the insulating section  20  and remain on the side of the insulating section  20  closer to the capacitors  10 . 
     The top-surface electrode layer  40  is located at the opposite side of the counter electrode layer  130  of the fifth capacitor  10 E as viewed from the support electrode layer  100  of the fifth capacitor  10 E, which is the capacitor  10  positioned farther toward the above-described side in the stacking direction than the other capacitors  10 . The top-surface electrode layer  40  is electrically connected to the counter electrode layer  130  of the fifth capacitor  10 E. The counter electrode layer  130  of the fifth capacitor  10 E and the top-surface electrode layer  40  are bonded to each other only with a conductive adhesive  30  interposed therebetween. In this embodiment, the extending direction of the top-surface electrode layer  40  is substantially the same as that of the support electrode layer  100  and the dielectric layer  120  of the first capacitor  10 A. 
     That is, in this embodiment, the counter electrode layer  130  of the second capacitor  10 B and the top-surface electrode layer  40  are electrically connected indirectly to each other via the fifth capacitor  10 E. 
     In the composite capacitor  2  according to the second embodiment of the invention, the support electrode layer  100  of the first capacitor  10 A and the top-surface electrode layer  40  are electrically connected to each other so as to be used as one terminal. The support electrode layer  100  of the second capacitor  10 B can be used as the other terminal. 
     In the circuit formed from one terminal to the other terminal of the composite capacitor  2  of this embodiment, the fourth capacitor  10 D is connected in series with the first capacitor  10 A, while the fifth capacitor  10 E is connected in series with the second capacitor  10 B. A set of the first capacitor  10 A and the fourth capacitor  10 D and a set of the second capacitor  10 B and the fifth capacitor  10 E are connected in parallel with each other. In this manner, in the composite capacitor  2  of this embodiment, the four capacitors  10  can be represented by two parallel-connection arrangements×two series-connection arrangements. 
     In the composite capacitor  2  according to the second embodiment of the invention, too, the second capacitor  10 B is connected in parallel with the first capacitor  10 A. Moreover, in the composite capacitor  2  according to the second embodiment of the invention, some of the plural capacitors  10  are connected in series with each other, thereby making it possible to enhance the withstand voltage. 
     Third Embodiment 
     Hereinafter, a composite capacitor according to a third embodiment of the invention will be described below. The composite capacitor according to the third embodiment of the invention is different from the composite capacitor  1  according to the first embodiment of the invention in that it further includes side conductors. An explanation of elements configured similarly to those of the first embodiment of the invention will not be repeated. 
       FIG. 13  is a sectional view of a composite capacitor according to the third embodiment of the invention. As shown in  FIG. 13 , a composite capacitor  3  according to the third embodiment of the invention further includes a first side electrode  50  and a second side electrode  60 . The first side electrode  50  is provided on the insulating section  20  at an opposite side of the insulating section  20  as viewed from the capacitor  10 . The second side electrode  60  is provided on the insulating section  20  at an opposite side of the insulating section  20  as viewed from the capacitor  10  so as to be separate from the first side electrode  50 . 
     The first side electrode  50  is connected to each of the support electrode layer  100  of the first capacitor  10 A and the support electrode layer  100  of the third capacitor  10 C. The second side electrode  60  is connected to each of the support electrode layer  100  of the second capacitor  10 B and the top-surface electrode layer  40 . 
     In this manner, the first side electrode  50  is electrically connected to each of the support electrode layer  100  of the first capacitor  10 A and the counter electrode layer  130  of the second capacitor  10 B. The second side electrode  60  is electrically connected to each of the counter electrode layer  130  of the first capacitor  10 A and the support electrode layer  100  of the second capacitor  10 B. 
     The above-described configuration makes it easy to mount the composite capacitor  3  on a mounting substrate so that the stacking direction of the plural capacitors  10  becomes perpendicular to the mounting substrate. More specifically, when the composite capacitor  3  is mounted in this manner, the first side electrode  50  can serve as one terminal of the composite capacitor  3 , while the second side electrode  60  can serve as the other terminal of the composite capacitor  3 . 
     Fourth Embodiment 
     A composite capacitor according to a fourth embodiment of the invention will be described below. The composite capacitor according to the fourth embodiment of the invention is different from the composite capacitor  3  according to the third embodiment of the invention mainly in that an insulating section surrounds the entirety of one capacitor. An explanation of elements configured similarly to those of the composite capacitor  3  of the third embodiment of the invention will not be repeated. 
       FIG. 14  is a sectional view of a composite capacitor according to the fourth embodiment of the invention. As shown in  FIG. 14 , in a composite capacitor  4  according to the fourth embodiment of the invention, plural capacitors  10  have the same configuration. 
     The composite capacitor  4  according to the present embodiment includes plural top-surface electrode layers  40 . Each of the plural top-surface electrode layers  40  is located at the opposite side of the counter electrode layer  130  of a corresponding one of the plural capacitors  10  as viewed from the support electrode layer  100  and is electrically connected to this counter electrode layer  130 . 
     In this embodiment, the insulating sections  20  are disposed to entirely surround the corresponding capacitors  10  and the corresponding top-surface electrode layers  40 . Because of this configuration, the insulating section  20  is located between the plural capacitors  10 . In each of the plural capacitors  10 , however, part of the top-surface electrode layer  40  is not covered with the insulating section  20  and is exposed, and part of the support electrode layer  100  is not covered with the insulating section  20  and is exposed in a direction different from the direction in which the top-surface electrode layer  40  is exposed. 
     In this embodiment, the first side electrode  50  and the second side electrode  60  are disposed to correspond to each of the plural capacitors  10 . In each of the plural capacitors  10 , the first side electrode  50  is electrically connected to the top-surface electrode layer  40 . The plural first side electrodes  50  are electrically connected to each other. Each of the second side electrodes  60  are electrically connected to the corresponding support electrode layer  100 . The plural second side electrodes  60  are electrically connected to each other. With this configuration, in the present embodiment, the second capacitor  10 B is connected in parallel with the first capacitor  10 A. 
     In the above-described embodiments, some of the configurations may be combined with each other within a technically possible range. 
     The above-disclosed embodiments are provided only for the purposes of illustration, but are not intended to be exhaustive or to limit the invention to the precise forms disclosed. It is intended that the scope of the invention be defined, not by the foregoing description, but by the following claims. The scope of the present invention is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions. 
     REFERENCE SIGNS LIST 
     
         
         
           
               1 ,  1   a ,  2 ,  3 ,  4 ,  9  composite capacitor 
               10  capacitor 
               10 A first capacitor 
               10 B second capacitor 
               10 C third capacitor 
               10 D fourth capacitor 
               10 E fifth capacitor 
               11  peripheral surface 
               20  insulating section 
               30  conductive adhesive 
               40  top-surface electrode layer 
               50  one-side electrode 
               60  other-side electrode 
               100  support electrode layer 
               100 X collective support electrode layer 
               110  columnar conductor 
               115  end portion 
               120  dielectric layer 
               130  counter electrode layer 
               200  substrate