Patent Publication Number: US-11049905-B2

Title: Memory device and memory system

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 16/402,838, filed May 3, 2019, which is a continuation of U.S. patent application Ser. No. 15/579,302, filed Dec. 4, 2017, now U.S. Pat. No. 10,319,787, which is a national stage application under 35 U.S.C. 371 and claims the benefit of PCT Application No. PCT/JP2016/064772 having an international filing date of May 18, 2016, which designated the United States, which PCT application claimed the benefit of Japanese Patent Application No. 2015-117228 filed Jun. 10, 2015, the disclosures of which are incorporated herein by reference in their entirety. 
    
    
     TECHNICAL FIELD 
     The disclosure relates to a memory device including a plurality of non-volatile storage sections, and to a memory system. 
     BACKGROUND ART 
     Up until now, a memory device including a plurality of non-volatile memory cells has been studied in terms of improvement in an integration degree of the memory cells. In recent years, in order to cope with still higher integration of the memory cells, a memory device has been proposed in which a plurality of memory cells are arrayed three-dimensionally (see, e.g., PTLs 1 to 3). 
     CITATION LIST 
     Patent Literature 
     
         
         PTL 1: Japanese Unexamined Patent Application Publication No. 2011-222994 
         PTL 2: International Publication No. WO 2012/070236 Specification 
         PTL 3: Japanese Unexamined Patent Application Publication No. 2011-114011 
       
    
     SUMMARY OF INVENTION 
     Incidentally, there have recently been increasing demands for still higher integration of the memory cells. 
     It is therefore desirable to provide a memory device having a structure suitable for still higher integration while ensuring easiness in production. Further, it is desirable to provide a memory system including such a memory device. 
     A memory device according to an embodiment of the disclosure is provided with n-number of memory cell units that are provided on a substrate and stacked in order as a first memory cell unit to an n-th memory cell unit in a first direction. The n-number of memory cell units each include one or more first electrodes, a plurality of second electrodes, a plurality of memory cells, and one or more lead lines. The plurality of second electrodes are each provided to intersect the first electrode. The plurality of memory cells are provided at respective intersections of the first electrode and the plurality of second electrodes. The plurality of memory cells are each coupled to both of the first electrode and the second electrode. The one or more lead lines are coupled to the first electrode to form one or more coupling parts. Here, the one or more coupling parts in an (m+1)-th (m denotes a natural number equal to or smaller than n) memory cell unit are located at a position where the one or more coupling parts and an m-th memory cell region surrounded by the plurality of memory cells in an m-th memory cell unit overlap each other in the first direction. In other words, the memory device allows a projection image in the m-th memory cell region in the first direction and a projection image in the coupling part in the (m+1)-th memory cell unit in the first direction to overlap each other. 
     A memory system according to an embodiment of the disclosure includes the above-described memory device and a controller that controls the memory device. 
     In the memory device and the memory system according to the respective embodiments of the disclosure, the one or more coupling parts in the (m+1)-th memory cell unit are located at the position where the one or more coupling parts and the memory cell region in the m-the memory cell unit overlap each other. Thus, it is possible to allow the memory device as a whole to have more memory cells in a predetermined space. 
     According to the memory device and the memory system as the respective embodiments of the disclosure, it becomes possible to achieve higher integration. It is to be noted that the effects of the disclosure are not limited to those described above, and may be any of effects described hereinafter. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a perspective view of an overall configuration example of a memory device according to a first embodiment of the disclosure. 
         FIG. 2  is an equivalent circuit diagram illustrating a portion of the memory device illustrated in  FIG. 1 . 
         FIG. 3  is an enlarged perspective view of an example of a selection transistor to be applied to the memory device illustrated in  FIG. 1 . 
         FIG. 4A  is an enlarged perspective view of a memory cell to be applied to the memory device illustrated in  FIG. 1 , together with its equivalent circuit diagram. 
         FIG. 4B  is an enlarged perspective view of another memory cell to be applied to the memory device illustrated in  FIG. 1 , together with its equivalent circuit diagram. 
         FIG. 5A  is a perspective view of one step in a manufacturing method of the memory device illustrated in  FIG. 1 . 
         FIG. 5B  is a cross-sectional view of one step subsequent to  FIG. 5A . 
         FIG. 5C  is a cross-sectional view of one step subsequent to  FIG. 5B . 
         FIG. 5D  is a cross-sectional view of one step subsequent to  FIG. 5C . 
         FIG. 5E  is a cross-sectional view of one step subsequent to  FIG. 5D . 
         FIG. 6  is a perspective view of a first modification example of the memory device according to the first embodiment of the disclosure. 
         FIG. 7  is an equivalent circuit diagram illustrating a portion of the memory device illustrated in  FIG. 6 . 
         FIG. 8  is an enlarged perspective view of an example of a memory cell to be applied to the memory device illustrated in  FIG. 6 . 
         FIG. 9  is a perspective view of a portion of the memory device illustrated in  FIG. 6 . 
         FIG. 10  is a perspective view of a second modification example of the memory device according to the first embodiment of the disclosure. 
         FIG. 11  is a perspective view of an overall configuration example of a memory device according to a second embodiment of the disclosure. 
         FIG. 12  is an enlarged perspective view of a memory cell to be applied to the memory device illustrated in  FIG. 11 , together with its equivalent circuit diagram. 
         FIG. 13  is a schematic cross-sectional view of a main part of the memory device illustrated in  FIG. 11 . 
         FIG. 14A  is a perspective view of one step in a manufacturing method of the memory device illustrated in  FIG. 11 . 
         FIG. 14B  is a cross-sectional view of one step subsequent to  FIG. 14A . 
         FIG. 14C  is a cross-sectional view of one step subsequent to  FIG. 14B . 
         FIG. 14D  is a cross-sectional view of one step subsequent to  FIG. 14C . 
         FIG. 14E  is a cross-sectional view of one step subsequent to  FIG. 14D . 
         FIG. 14F  is a cross-sectional view of one step subsequent to  FIG. 14E . 
         FIG. 14G  is a cross-sectional view of one step subsequent to  FIG. 14F . 
         FIG. 14H  is a cross-sectional view of one step subsequent to  FIG. 14G . 
         FIG. 14J  is a cross-sectional view of one step subsequent to  FIG. 14H . 
         FIG. 14K  is a cross-sectional view of one step subsequent to  FIG. 14J . 
         FIG. 14L  is a cross-sectional view of one step subsequent to  FIG. 14K . 
         FIG. 15  is a perspective view of an overall configuration example of a memory device according to a third embodiment of the disclosure. 
         FIG. 16  is an enlarged perspective view of a memory cell to be applied to the memory device illustrated in  FIG. 15 , together with its equivalent circuit diagram. 
         FIG. 17A  is a perspective view of one step in a manufacturing method of the memory device illustrated in  FIG. 15 . 
         FIG. 17B  is a cross-sectional view of one step subsequent to  FIG. 17A . 
         FIG. 17C  is a cross-sectional view of one step subsequent to  FIG. 17B . 
         FIG. 17D  is a cross-sectional view of one step subsequent to  FIG. 17C . 
         FIG. 17E  is a cross-sectional view of one step subsequent to  FIG. 17D . 
         FIG. 17F  is a cross-sectional view of one step subsequent to  FIG. 17E . 
         FIG. 17G  is a cross-sectional view of one step subsequent to  FIG. 17F . 
         FIG. 18A  is a schematic cross-sectional view of a main part of the memory device illustrated in  FIG. 15 . 
         FIG. 18B  is another schematic cross-sectional view of the main part of the memory device illustrated in  FIG. 15 . 
         FIG. 19  describes an outline configuration of a memory system that includes the memory device of the disclosure. 
     
    
    
     MODES FOR CARRYING OUT THE INVENTION 
     In the following, some embodiments of the disclosure are described in detail with reference to drawings. It is to be noted that description is given in the following order. 
     1. First Embodiment (A memory device in which a plurality of WLs are disposed stepwise) 
     2. Modification Example 1 (First Modification Example of First Embodiment) 
     3. Modification Example 2 (Second Modification Example of First Embodiment) 
     4. Second Embodiment (A memory device including a resistance change element having substantially same planar shape as that of WL) 
     5. Third Embodiment (Another memory device including a resistance change element having the substantially same planar shape as that of WL) 
     6. Application Example (A memory system including a memory device) 
     1. First Embodiment 
     [Configuration of Memory Device  1 ] 
       FIG. 1  is a perspective view of an overall configuration example of a memory device  1  according to a first embodiment of the disclosure. Further,  FIG. 2  is an equivalent circuit diagram illustrating a portion of the memory device  1  of  FIG. 1 . 
     The memory device  1  is a non-volatile storage having a three-dimensional structure, and includes, on a semiconductor substrate  2  (hereinafter, referred to simply as substrate  2 ), n-number of memory cell units MU. The semiconductor substrate  2  has a principal surface that extends in an X-axis direction and in a Y-axis direction. In the n-number of memory cell units MU, a first memory cell unit to an n-th memory cell unit are stacked in order in a Z-axis direction.  FIGS. 1 and 2  illustrate a case of n=4, i.e., a case where four memory cell units MU 1  to MU 4  are stacked in order. In addition,  FIG. 2  illustrates only a portion of the four memory cell units MU 1  to MU 4 . 
     The n-number of memory cell units MU each include one plate-shaped electrode WL, a plurality of columnar electrodes BL, a plurality of memory cells MC, and a lead line  4 . The plurality of columnar electrodes BL are each provided to intersect the plate-shaped electrode WL. The plurality of memory cells MC are provided at respective intersections of the plate-shaped electrode WL and the plurality of columnar electrodes BL, and are each coupled to both of the plate-shaped electrode WL and the columnar electrode BL. The lead line  4  is coupled to the plate-shaped electrode WL to form a coupling part  3 . The plate-shaped electrode WL extends along an X-Y plane, and is provided in common for the plurality of columnar electrodes BL that form each memory cell unit MU. The plurality of columnar electrodes BL each standing from the plate-shaped electrode WL toward the substrate  2 . It is to be noted that, here, the columnar electrodes BL that are in a mutually overlapping position in the Z-direction, among the plurality of columnar electrodes BL provided in the memory cell units MU 1  to MU 4 , are linked together by penetration of the plate-shaped electrode WL. Further, in the X-Y plane, the plate-shaped electrode WL(m+1) in the (m+1)-th memory cell unit MU(m+1) has an occupation area that is smaller than an occupation area of the plate-shaped electrode WLm in the m-th memory cell unit MUm. That is, the plate-shaped electrode WL 2  in the memory cell unit MU 2  has an occupation area that is smaller than an occupation area of the plate-shaped electrode WL 1  in the memory cell unit MU 1 . The plate-shaped electrode WL 3  in the memory cell unit MU 3  has an occupation area that is smaller than an occupation area of the plate-shaped electrode WL 2  in the memory cell unit MU 2 . The plate-shaped electrode WL 3  in the memory cell unit MU 3  has an occupation area that is smaller than an occupation area of the plate-shaped electrode WL 2  in the memory cell unit MU 2 . The plate-shaped electrode WL 4  in the memory cell unit MU 4  has an occupation area that is smaller than an occupation area of the plate-shaped electrode WL 3  in the memory cell unit MU 3 . In this manner, an occupation area of the plate-shaped electrode WL becomes gradually smaller as the plate-shaped electrode WL is away from the substrate  2  to form a stepped structure as a whole. 
     A plurality of selection transistors Tr that each serve as a depletion (Depletion) transistor are provided, between the first (i.e., lowermost layer) memory cell unit MU 1  and the substrate  2 , on extensions of the respective columnar electrodes BL.  FIG. 3  is an enlarged perspective view of a configuration example of the selection transistor Tr (right side in the drawing), together with its corresponding equivalent circuit diagram (left side in the drawing). As illustrated in  FIG. 3 , at the lower part of the memory cell unit MU 1 , there are provided a plurality of gate selection lines GSL that extend in the X-axis direction, and are arranged in the Y-axis direction. Further, at the lower part of the plurality of gate selection lines GSL, there are provided a plurality of source lines SL that extend in the Y-axis direction, and are arranged in the X-axis direction. At each of intersections of the plurality of gate selection lines GSL and the plurality of source lines SL, there is provided a contact line CL that links the gate selection line GSL and the source line SL to each other. Further, a columnar electrode BL 1  of the lowermost-layer memory cell unit MU 1  penetrates the gate selection line GSL to be brought into contact with the contact line CL. However, the columnar electrode BL 1  and the gate selection line GSL are electrically insulated from each other by an insulating layer Z 1  provided therebetween. 
     As a constituent material of the source line SL, metal containing Cu, Al, or W, for example, is preferable. Alternatively, a material with electric conductivity containing one or more elements of C, Si, Ge, In, and Ga (e.g., a carbon nanotube, activated polysilicon, etc.) may also be used. Further, it is also possible for other various wiring lines and various electrodes such as the gate selection line GSL, the plate-shaped electrode WL, and the columnar electrode BL to be made of a material similar to the constituent material of the source line SL, unless otherwise stated. 
     As illustrated in  FIG. 1 , the plurality of memory cell units MU (MU 1  to MU 4 ) include, respectively, memory cell regions MR (MR 1  to MR 4 ) and peripheral regions PR (PR 1  to PR 4 ). The memory cell region MR is a region occupied by the plurality of memory cells MC. More specifically, the memory cell region MR refers to a region surrounded by a virtual line (region surrounded by a broken line in  FIG. 1 ) that sequentially links several memory cells MC located outermost within the X-Y plane, among all the memory cells MC included in each memory cell unit MU. In contrast, the peripheral region PR refers to a remaining region excluding the memory cell region MR, out of a region occupied by the plate-shaped electrode WL that forms each memory cell unit MU. 
       FIG. 4A  illustrates an enlarged perspective view of a configuration example of the memory cell MC (right side in the drawing), together with its corresponding equivalent circuit diagram (left side in the drawing).  FIG. 4A  illustrates, as a representative, a vicinity of any given one memory cell MC in the first memory cell unit MU 1 . As illustrated in  FIG. 4A , the columnar electrode BL 1  of the lowermost-layer memory cell unit MU 1  penetrates the plate-shaped electrode WL 1  in the Z-axis direction. Other memory cell units MU 2  to MU  4  also have similar configurations. That is, the columnar electrode BL 2  penetrates the plate-shaped electrode WL 2  in the Z-axis direction; the columnar electrode BL 3  penetrates the plate-shaped electrode WL 3  in the Z-axis direction; and the columnar electrode BL 4  penetrates the plate-shaped electrode WL 4  in the Z-axis direction. However, the columnar electrodes BL 1  to BL 4  and the plate-shaped electrodes WL 1  to BL are separated, respectively, from each other by a resistance change element VR as the memory cell MC provided to be interposed therebetween. It is to be noted that, as illustrated in  FIG. 4B , each memory cell MC mounted in the memory device  1  may have a configuration in which a selection element SEL is inserted between the columnar electrode BL 1  and the resistance change element VR. In any memory cell MC illustrated in  FIGS. 4A and 4B , an access current is applied between the source line SL and the plate-shaped electrode WL, and a voltage of the gate selection line GSL is controlled to impart an access pulse to the resistance change element VR to enable a resistance state thereof to be changed or to be read. However, the selection element SEL in  FIG. 4B  serves to prevent erroneous access to a non-selected resistance change element VR by causing a current to flow to the resistance change element VR only when an access pulse greater than a certain voltage is applied. 
     The resistance change element VR is configured by a stacked structure of an ion supply layer and an insulating layer, for example. Examples of a material of the ion supply layer include a metal film containing one or more metal elements selected from Cu, Ag, Zr, and Al, an alloy film (e.g., CuTe alloy film), and a metal compound film. It is to be noted that metal elements other than Cu, Ag, Zr, and Al may also be used as long as the metal elements have an easily-ionizable property. Further, it is desirable that an element to be combined with one or more of Cu, Ag, Zr, and Al be an element of one or more of S, Se, and Te. Furthermore, examples of a constituent material of the insulating layer in the resistance change element VR include SiN, SiO 2 , and Gd 2 O 3 . 
     In the memory device  1 , a size of an (m+1)-th memory cell region MR(m+1) in the (m+1)-th memory cell unit MU(m+1) is narrower than a size of the m-th memory cell region MRm. Further, the number of the plurality of memory cells MC (number of columnar electrodes BL(m+1)) in the (m+1)-th memory cell unit MU(m+1) is smaller than number of the plurality of memory cells MC (number of columnar electrode BLm) in the m-th memory cell unit MUm. In the example of  FIG. 1 , the memory cell region MR 1  in the memory cell unit MU 1  has a total of 80 memory cells MC and 80 columnar electrodes BL 1  that are disposed (to have 10 pieces in the X direction and 8 pieces in the Y direction). In contrast, the memory cell region MR 2  in the memory cell unit MU 2  has a total of 70 memory cells MC and 70 columnar electrodes BL 2  that are disposed (to have 10 pieces in the X direction and 7 pieces in the Y direction). Further, the memory cell region MR 3  in the memory cell unit MU 3  has a total of 60 memory cells MC and 60 columnar electrodes BL 3  that are disposed (to have 10 pieces in the X direction and 6 pieces in the Y direction). Furthermore, the memory cell region MR 4  in the memory cell unit MU 4  has a total of 50 memory cells MC and 50 columnar electrodes BL 4  that are disposed (to have 10 pieces in the X direction and 5 pieces in the Y direction). 
     A lead line LL (LL 1  to LL 4 ) includes a contact pillar CP (CP 1  to CP 4 ) and a beam CB (CB 1  to CB 4 ). The contact pillar CP (CP 1  to CP 4 ) forms the coupling part  3  with respect to the first electrode WL, and extends upward from the coupling part  3 , i.e., in a direction away from the substrate  2 . The beam CB (CB 1  to CB 4 ) is coupled to an upper end of the contact pillar CP (CP 1  to CP 4 ), and extends within the X-Y plane (in Y-axis direction in  FIG. 1 ). The other end of the beam CB is coupled to a drive circuit  4 . The drive circuit  4  is embedded in the substrate  2 , for example, and executes a writing operation into a desired memory cell MC and a reading operation from the desired memory cell MC. The drive circuit  4  adjusts, on the basis of a control signal from the outside, for example, a voltage to be applied to the plate-shaped electrode WL, the columnar electrode BL, and the gate selection line of the selection transistor Tr that correspond to the desired memory cell MC. It is to be noted that a plurality of lead lines LL (LL 1  to LL 4 ) may be provided for one plate-shaped electrode WL (WL 1  to WL 4 ). 
     One or more coupling parts  3  in the (m+1)-th memory cell unit MU(m+1) are located at a position where a peripheral region PR(m+1) and the m-th memory cell region MRm surrounded by the plurality of memory cells MC in the m-th memory cell unit MUm overlap each other in the Z-axis direction. That is, the coupling part  3  in the memory cell unit MU 2  is located at a position where the peripheral region PR 2  and the memory cell region MR 1  overlap each other in the Z-axis direction. The coupling part  3  in the memory cell unit MU 3  is located at a position where the peripheral region PR 3  and the memory cell region MR 2  overlap each other in the Z-axis direction. The coupling part  3  in the memory cell unit MU 4  is located at a position where the peripheral region PR 4  and the memory cell region MR 3  overlap each other in the Z-axis direction. In  FIG. 1 , in particular, the coupling part  3  in the (m+1)-th memory cell unit MU(m+1) is located at a position where the coupling part  3  and any of the plurality of memory cells MC in the m-th memory cell unit MUm overlap each other in the Z-axis direction. 
     [Manufacturing Method of Memory Device  1 ] 
     The memory device  1  is able to be manufactured as follows, for example. 
       FIGS. 5A to 5E  illustrate a portion of a manufacturing method of the memory device  1  in order of steps. First, as illustrated in  FIG. 5A , the substrate  2  having a principal surface  2 S along the X-Y plane is prepared, and the drive circuit  4  (not illustrated here) is formed on the principal surface  2 S. Thereafter, the plurality of source lines SL extending in the Y-axis direction are formed, on the substrate  2 , to be arranged in the X-axis direction. 
     Next, an insulating layer (not illustrated) made of SiO 2  is formed all over to cover the plurality of source lines SL. Thereafter, as illustrated in  FIG. 5B , the plurality of gate selection lines GSL extending in the X-axis direction and arranged in the Y-axis direction are formed to intersect the plurality of source lines SL. Further, at respective intersections of the plurality of source lines SL and the plurality of gate selection lines GSL that overlap each other in the Z-axis direction, through-holes K are formed that each penetrate the gate selection line GSL and the insulating layer (insulating layer interposed between the source line SL and the gate selection line GSL) immediately therebelow. Each of the through-holes reaches an upper surface of the source line SL. Thereafter, the insulating layer Z 1  (see  FIG. 3 ) is formed to cover an inner wall surface of each of the through-holes K, following which the inside of each of the through-holes K is filled with a predetermined electrically-conductive material to form the contact line CL. 
     Subsequently, as illustrated in  FIG. 5C , the plate-shaped electrode WL 1  is formed to cover all the columnar electrodes BL 1 . In this situation, the plate-shaped electrode WL 1  is formed to have such a size that the plate-shaped electrode WL 1  includes the peripheral region PR 1  on the periphery of the memory cell region MR 1  that is to form the plurality of memory cells MC. Further, through-holes (not illustrated) are provided at respective positions, of the plate-shaped electrode WL 1 , corresponding to a plurality of contact lines CL positioned below. Thereafter, the resistance change element VR is formed to cover the inner wall surface of each of the through-holes, and the inside of each of the through-holes is filled with a predetermined electrically-conductive material, thereby forming the plurality of columnar electrodes BL 1  to allow for coupling to the respective contact lines CL (see  FIG. 4A ). This completes the memory cell unit MU 1  in which the plurality of memory cells MC are provided in the memory cell region MR 1 . 
     Subsequently, as illustrated in  FIG. 5D , the plate-shaped electrode WL 2  is formed above the plate-shaped electrode WL 1 . In this situation, a size of the plate-shaped electrode WL 2  in the Y-axis direction is made smaller than a size of the plate-shaped electrode WL 1  in the Y-axis direction in order to prevent the plate-shaped electrode WL 2  from overlapping the peripheral region PR 1 . Further, through-holes are provided at respective positions, of the plate-shaped electrode WL 2 , corresponding to the plurality of columnar electrodes BL 1  positioned below. Thereafter, the resistance change element VR is formed to cover the inner wall surface of each of the through-holes, and the inside of each of the through-holes is filled with a predetermined electrically-conductive material, thereby forming the plurality of columnar electrodes BL 2  to allow for coupling to the respective columnar electrodes BL 1 . This completes the memory cell unit MU 2  in which the plurality of memory cells MC are provided in the memory cell region MR 2 . 
     Thereafter, similar operations are repeated to form the memory cell unit MU 3  and the memory cell unit MU 4  in order, as illustrated in  FIG. 5E . In this manner, after the stepwise formation of the plate-shaped electrodes WL 1  to WL 4 , the contact pillars CP 1  to CP 4  are collectively formed to stand, respectively, in the peripheral regions PR 1  to PR 4  of the plate-shaped electrodes WL 1  to WL 4 . Further, the beams CB 1  to CB 4  are collectively formed to be coupled to the upper ends of the contact pillars CP 1  to CP 4 , respectively. This allows the lead lines LL 1  to LL 4  to be obtained. 
     This completes the memory device  1 . 
     [Workings and Effects of Memory Device  1 ] 
     In the memory device  1 , the coupling part  3  in the (m+1)-th memory cell unit MU(m+1) is located at a position where the coupling part  3  and the memory cell region MRm in the m-th memory cell unit Mm overlap each other in the Z-axis direction. In other words, the memory cells MC that form the memory cell unit MUm are also disposed below the peripheral region PR(m+1) where the coupling part  3  is provided in the memory cell unit MU(m+1). This enables the memory device  1  as a whole to utilize a space efficiently and thus to include more memory cells MC in a predetermined space. Thus, it becomes possible to achieve higher integration. 
     2. Modification Example 1 
       FIG. 6  is a perspective view of an overall configuration example of a memory device  1 A according to a second modification example of the foregoing memory device  1 . Further,  FIG. 7  is an equivalent circuit diagram illustrating a portion of the memory device  1 A of  FIG. 6 . Furthermore,  FIG. 8  is an enlarged perspective view of a configuration example of the memory cell MC (right side in the drawing), together with its corresponding equivalent circuit diagram (left side in the drawing). 
     The memory device  1 B includes a plurality of first linear electrodes  21  and a plurality of second linear electrodes  22  instead of the plate-shaped electrodes WL in each of the memory cell units MU 1  to MU 4 . The first linear electrodes  21  and the second linear electrodes  22  each extend in the Y-axis direction, and are arranged alternately in the X-axis direction. Further, columnar electrodes (BL 1  to BL 4 ) are each interposed between the first linear electrode  21  and the second linear electrode  22  that are adjacent to each other in the X-axis direction, in each of the memory cell units MU 1  to MU 4 . Furthermore, as illustrated in  FIG. 8 , the memory cell MC is configured by the resistance change element VR that is interposed between the columnar electrode BL and the first linear electrode  21  and between the columnar electrode BL and the second linear electrode  22 . It is to be noted that illustration of the resistance change element VR is omitted in  FIG. 6 . 
     Further, as illustrated in  FIG. 6 , lead lines  25  and  28  are provided instead of the lead line LL. The lead line  25  includes a first contact pillar  23  and a first beam  24 . The first contact pillar  23  is coupled to the first linear electrodes  21  to form a first coupling part  3 A. The first beam  24  is coupled to an upper end of the first contact pillar  23 , and extends in the X-axis direction, for example. In contrast, the lead line  28  includes a second contact pillar  26  and a second beam  27 . The second contact pillar  26  is coupled to the second linear electrodes  22  to form a second coupling part  3 B. The second beam  27  is coupled to an upper end of the second contact pillar  26 , and extends in the X-axis direction, for example. It is to be noted that, in each of the memory cell units MU 1  to MU 4 , a plurality of first contact pillars  23  coupled to the respective first linear electrodes  21  are coupled in common to a single first beam  24 . Likewise, in each of the memory cell units MU 1  to MU 4 , a plurality of second contact pillars  26  coupled to the respective second linear electrodes  22  are coupled in common to a single first beam  27 . 
     The memory device  1 B includes the plurality of gate selection lines GSL arranged in the Y-axis direction and extending in the X-axis direction; each of the plurality of gate selection lines GSL is coupled to the plurality of columnar electrodes BL arranged in the X-axis direction. 
       FIG. 9  illustrates a configuration of a main part of the memory device  1 B in which the first beam  24  and the second beam  27  are omitted. As illustrated in  FIG. 9 , the first linear electrodes  21  and the second linear electrodes  22  are each disposed stepwise. That is, a size of the first linear electrode  21  in the (m+1)-th memory cell unit MU(m+1) in the Y-axis direction is shorter than a size of the first linear electrode  21  in the m-th memory cell unit MUm in the Y-axis direction. Likewise, a size of the second linear electrode  22  in the memory cell unit MU(m+1) in the Y-axis direction is shorter than a size of the second linear electrode  22  in the memory cell unit MUm in the Y-axis direction. Such a configuration allows a region where the plurality of first contact pillars  23  and the plurality of second contact pillars  26  stand and the memory cell region where the memory cells MC are provided to overlap each other in the Z-axis direction. Thus, it becomes possible to achieve higher integration also in the memory device  1 A, similarly to the memory device  1  of the foregoing first embodiment. 
     3. Modification Example 2 
       FIG. 10  is a perspective view of an overall configuration example of a memory device  1 B that is a second modification example of the above-described memory device  1 . In the memory device  1  of the foregoing first embodiment, every time a single plate-shaped electrode WL is stacked, the through-holes are opened in the plate-shaped electrode WL to perform formation of the memory cells MC and the columnar electrodes BL. In contrast, as in the present modification example, formation of common through-holes may be performed for the plurality of plate-shaped electrodes WL after the plurality of plate-shaped electrodes WL are stacked, in order to further simplify the manufacturing process. In this case, it is possible to perform collective formation of the memory cells MC and the columnar electrodes BL throughout the plurality of the memory cell units MU. In  FIG. 10 , two plate-shaped electrodes WL are stacked, and thereafter the collection formation of the through-holes are performed for the two plate-shaped electrodes WL, following which the formation of the memory cells MC and the columnar electrodes BL are further performed to fill the through-holes. It is to be noted that the formation of the common through-holes may be performed for plate-shaped electrodes WL of three layers or more. 
     4. Second Embodiment 
     [Configuration of Memory Device  1 B] 
       FIG. 11  is a perspective view of an overall configuration example of a memory device  1 B as a second embodiment of the disclosure.  FIG. 12  is an enlarged perspective view of a vicinity of the memory cell MC to be applied to the memory device  1 B illustrated in  FIG. 11 , together with its equivalent circuit diagram. Further,  FIG. 13  is a schematic cross-sectional view of a main part of the memory device  1 B. 
     As illustrated in  FIGS. 11 to 13 , in the memory device  1 B, a plurality of bit lines BL, the plurality of memory cells MC, and a plurality of word lines WL are stacked in order from side of the substrate  2  (illustrated only in  FIG. 13 ) in the Z-axis direction. More specifically, a bit line BL 0 , the memory cell MC, a word line WL 0 , the memory cell MC, a bit line BL 1 , the memory cell MC, a word line WL 1 , the memory cell MC, a bit line BL 2 , . . . are stacked in order over the substrate  2 . The memory cell MC has a stacked structure in which the selection element SEL and the resistance change element VR are stacked in order from side of the substrate  2 . Further, the resistance change element VR has substantially the same planar shape as that of the word line WL or the bit line BL immediately above the resistance change element VR. 
     The plurality of word lines WL each extend in substantially the X-axis direction, and are disposed to be arranged in the Y-axis direction. The plurality of bit lines BL each extend in substantially the Y-axis direction, and are disposed to be arranged in the X-axis direction. A plurality of selection elements SEL are disposed to be arranged in both of the X-axis direction and the Y-axis direction. One resistance change element VR is provided in common for the plurality of selection elements SEL arranged in the X-axis direction, or is provided in common for the plurality of selection elements SEL arranged in the Y-axis direction. 
     Also in the present embodiment, the (m+1)-th memory cell region MR(m+1) surrounded by the plurality of memory cells MC in the (m+1)-th memory cell unit is narrower than the m-th memory cell region MRm. Further, as the lead line, there are provided a first contact pillar  31  and a second contact pillar  32 . The first contact pillar  31  is coupled to the word line WL to form a first coupling part  30 A as the coupling part, and extends to be away from the substrate  2 . The second contact pillar  32  is coupled to the bit line BL to form a second coupling part  30 B as the coupling part, and extends to be away from the substrate  2 . 
     An upper end of the first contact pillar  31  is coupled to the drive circuit  4  through a wiring line  41  that includes a beam  41 A and a pillar  41 B. Further, an upper end of the second contact pillar  32  is coupled to the drive circuit  4  through a wiring line  42  that includes a beam  42 A and a pillar  42 B. 
     [Manufacturing Method of Memory Device  1 B] 
     The memory device  1 B is able to be manufactured as follows, for example. 
       FIGS. 14A to 14L  illustrate a portion of a manufacturing method of the memory device  1 B in order of steps. First, as illustrated in  FIG. 14A , the substrate  2  having a principal surface  2 S along the X-Y plane is prepared, and the drive circuit  4  (not illustrated here) is formed on the principal surface  2 S. Thereafter, the plurality of contact lines CL stand on the substrate  2 , following which a plurality of bit lines BL 0  extending in the Y-axis direction are formed to be arranged in the X-axis direction to be coupled to the contact lines CL. 
     Next, as illustrated in  FIG. 14B , the plurality of selection elements SEL are formed into matrix as a whole in the memory cell region MR (MR 1 ). Here, the plurality of selection elements SEL stand to be arranged at equal intervals, for example, in the Y-axis direction for one bit line BL 0 . Both adjacent regions extended from the memory cell region MR along the Y-axis direction are each referred to as the peripheral region (or contact region) PR (PR 1 ). In the peripheral region PR, a portion of the bit line BL 0  has a bent part having a larger width. This is aimed at allowing for disposition of the contact line CL having a larger diameter than a width of the bit line BL 0 . It is to be noted that the bit line BL 0  ends midway in  FIGS. 14A to 14L , but is coupled to another memory cell block MB (described later) disposed adjacently. Basically, one contact line CL drives respective bit lines BL 0  in two memory cell units. This is why the contact lines are disposed only for four bit lines BL 0  among eight bit lines BL 0 , although the eight bit lines BL 0  are drawn in  FIG. 14A , for example. The remaining four bit lines BL 0  where the contact line CL is not disposed are each coupled to the bit line BL 0  that extends from the adjacent memory cell block MB, and are driven. 
     Next, as illustrated in  FIG. 14C , as an upper layer of the selection elements SEL, the resistance change element VR and the word line WL 0  are stacked in order all over, and thereafter are patterned collectively to have a plurality of (eight as an example in  FIG. 14C ) linear patterns extending in substantially the X-axis direction. In this situation, a stacked pattern P 0  extending in the X-axis direction is coupled in common to the plurality of selection elements SEL arranged in the X-axis direction. The stacked pattern P 0  is a stacked structure of the resistance change element VR and the word line WL 0 . It is to be noted that, in  FIG. 14C , only one of eight stacked patterns P 0  is drawn to have the stacked structure of the resistance change element VR and the word line WL 0 ; however, each of other stacked patterns P 0  also has a similar structure. 
     Next, as illustrated in  FIG. 14D , the plurality of selection elements SEL are provided in matrix on each of the stacked patterns P 0 .  FIG. 14D  illustrates an example in which four selection elements SEL are disposed on each of the stacked patterns P 0 . The memory cell region MR 2  in this situation is narrower than the memory cell region MR 1  ( FIG. 14B ). 
     Next, as illustrated in  FIG. 14E , as an upper layer of the selection elements SEL, the resistance change element VR and the bit line BL 1  are stacked in order all over, and thereafter are patterned collectively to have a plurality of (four as an example in  FIG. 14E ) linear patterns extending in substantially the Y-axis direction. In this situation, a stacked pattern P 1  extending in the Y-axis direction is coupled in common to the plurality of selection elements SEL arranged in the Y-axis direction. The stacked pattern P 1  is a stacked structure of the resistance change element VR and the bit line BL 1 . It is to be noted that, in  FIG. 14E , only one of four stacked patterns P 1  is drawn to have the stacked structure of the resistance change element VR and the bit line BL 1 ; however, each of other stacked patterns P 1  also has a similar structure. 
     Next, as illustrated in  FIG. 14F , the plurality of selection elements SEL are provided in matrix on each of the stacked patterns P 1 .  FIG. 14F  illustrates an example in which four selection elements SEL are disposed on each of the stacked patterns P 1 . The memory cell region MR 3  in this situation is still narrower than the memory cell region MR 2  ( FIG. 14D ). 
     Next, as illustrated in  FIG. 14G , as an upper layer of the selection elements SEL, the resistance change element VR and the word line WL 1  are stacked in order all over, and thereafter are patterned collectively to have a plurality of (four as an example in  FIG. 14G ) linear patterns extending in substantially the X-axis direction. In this situation, a stacked pattern P 2  extending in the X-axis direction is coupled in common to the plurality of selection elements SEL arranged in the X-axis direction. The stacked pattern P 2  is a stacked structure of the resistance change element VR and the word line WL 1 . It is to be noted that, in  FIG. 14G , only one of four stacked patterns P 2  is drawn to have the stacked structure of the resistance change element VR and the word line WL 1 ; however, each of other stacked patterns P 2  also has a similar structure. 
     Next, as illustrated in  FIG. 14H , the plurality of selection elements SEL are provided in matrix on each of the stacked patterns P 2 .  FIG. 14H  illustrates an example in which four selection elements SEL are disposed on each of the stacked patterns P 2 . The memory cell region MR 4  in this situation is equivalent to the memory cell region MR 3  ( FIG. 14F ). 
     Next, as illustrated in  FIG. 14J , as an upper layer of the selection elements SEL, the resistance change element VR and the bit line BL 2  are stacked in order all over, and thereafter are patterned collectively to have a plurality of (four as an example in  FIG. 14J ) linear patterns extending in substantially the Y-axis direction. In this situation, a stacked pattern P 3  extending in the X-axis direction is coupled in common to the plurality of selection elements SEL arranged in the Y-axis direction. The stacked pattern P 3  is a stacked structure of the resistance change element VR and the bit line BL 2 . It is to be noted that, in  FIG. 14J , only one of four stacked patterns P 3  is drawn to have the stacked structure of the resistance change element VR and the bit line BL 2 ; however, each of other stacked patterns P 3  also has a similar structure. 
     Next, as illustrated in  FIG. 14K , a plurality of first contact pillars  31  extending upward from the word line WL and a plurality of second contact pillars  32  extending upward from the bit line BL are formed. In addition, a plurality of pillars  41 B and a plurality of pillars  42 B each coupled to the drive circuit  4  (see  FIG. 11 ) are formed. It is to be noted that, in  FIG. 14K , the substrate  2  and the drive circuit  4  illustrated in  FIG. 11  are omitted. 
     Finally, as illustrated in  FIG. 14L , a plurality of beams  41 A are formed that each link the first contact pillar  31  and the pillar  41 B to each other, and a plurality of beams  42 A are formed that each link the second contact pillar  32  and the pillar  42 B to each other. It is to be noted that, in  FIG. 14L , the substrate  2  and the drive circuit  4  illustrated in  FIG. 11  are omitted. 
     This completes the memory device  1 B. 
     [Workings and Effects of Memory Device  1 B] 
     The memory device  1 B also allows the peripheral region PR and the memory cell region MR located at a level different therefrom to overlap each other, thus making it possible to utilize a space efficiently and thus to include more memory cells MC in a predetermined space. Thus, it becomes possible to achieve higher integration. Further, the resistance change element VR has substantially the same planar shape as that of the word line WL or the bit line BL immediately above the resistance change element VR, thus making it possible to simplify the manufacturing process. 
     5. Third Embodiment 
     [Configuration of Memory Device  1 C] 
       FIG. 15  is a perspective view of an overall configuration example of a memory device  1 C as a third embodiment of the disclosure.  FIG. 16  is an enlarged perspective view of a vicinity of the memory cell MC to be applied to the memory device  1 C illustrated in  FIG. 15 , together with its equivalent circuit diagram. In the memory device  1 B of the foregoing second embodiment, the memory cells MC of four layers are formed between the bit lines BL of three layers and the word lines WL of two layers. In a case of such a configuration, three layers of the word line WL 0 , the bit line BL 1 , and the word line WL 1  are coupled to the memory cells MC of two layers. In a cross-point memory, a leak current flows also to a non-selected memory cell MC; thus, there is a possibility that larger load may be applied to the drive circuit  4  when the number of levels of the memory cell MC is increased. Accordingly, in the memory device  1 C of the present embodiment, a structure is attained, in which the memory device  1 C includes the memory cells MC, the bit lines BL, and the word lines WL that have the same number of levels and in which each bit line BL and each word line WL are coupled only to the memory cells MC of one layer. 
     Specifically, as illustrated in  FIGS. 15 to 16 , in the memory device  1 C, the word line WL 0 , the memory cell MC, the bit line BL 0 , the insulating layer, the word line WL 1 , the memory cell MC, the bit line BL 1  are stacked in order over the substrate  2  in the Z-axis direction. The memory cell MC has a stacked structure in which the selection element SEL and the resistance change element VR are stacked in order from side of the substrate  2 . Further, the resistance change element VR has substantially the same planar shape as that of the bit line BL immediately above the resistance change element VR. Further, the memory device  1 C includes a contact pillar  51  that is coupled to the word line WL 1  and extends downward (toward the substrate  2 ). Except this point, the memory device  1 C has configurations substantially similar to those of the memory device  1 B of the second embodiment. 
     [Manufacturing Method of Memory Device  1 C] 
     The memory device  1 C is able to be manufactured as follows, for example. 
       FIGS. 17A to 17G  illustrate a portion of a manufacturing method of the memory device  1 C in order of steps. First, as illustrated in  FIG. 17A , the plurality of contact lines CL stand, following which a plurality of word lines WL 0  extending in the Y-axis direction are formed to be arranged in the X-axis direction to be coupled to the contact lines CL. 
     Next, as illustrated in  FIG. 17B , the plurality of selection elements SEL are formed into matrix as a whole in the memory cell region MR (MR 1 ). Here, the plurality of (four in an example of  FIG. 17B ) selection elements SEL stand to be arranged at equal intervals, for example, in the Y-axis direction for one bit line BL 0 . Both adjacent regions extended from the memory cell region MR along the Y-axis direction are each referred to as the peripheral region (or contact region) PR (PR 1 ). In the peripheral region PR, a portion of the word line WL 0  has a bent part having a larger width. This is aimed at allowing for disposition of the contact line CL having a larger diameter than a width of the word line WL 0 . 
     Next, as illustrated in  FIG. 17C , as an upper layer of the selection elements SEL, the resistance change element VR and the bit line BL 0  are stacked in order all over, and thereafter are patterned collectively to have a plurality of linear patterns extending in substantially the X-axis direction. In this situation, the resistance change element VR extending in the X-axis direction is coupled in common to the plurality of selection elements SEL arranged in the X-axis direction. Further, the contact pillar  51  is formed that is coupled to the word line WL 1  to be formed thereafter. 
     Next, the insulating layer (not illustrated) is formed all over, and thereafter a plurality of word lines WL 1  extending in substantially the Y-axis direction are formed, as illustrated in  FIG. 17D . In this situation, the word line WL 1  is formed to be coupled to an upper end of the contact pillar  51 . 
     Next, as illustrated in  FIG. 17E , the plurality of selection elements SEL are provided in matrix on each of the word lines WL 1 . 
     Next, as illustrated in  FIG. 17F , as an upper layer of the selection elements SEL, the resistance change element VR and the bit line BL 1  are stacked in order all over, and thereafter are patterned collectively to have a plurality of linear patterns extending in substantially the X-axis direction. In this situation, the resistance change element VR extending in the X-axis direction is coupled in common to the plurality of selection elements SEL arranged in the X-axis direction. 
     Next, as illustrated in  FIG. 17G , a plurality of contact pillars  52 A and a plurality of contact pillars  52 B are formed that extend upward, respectively, from the bit line BL 0  and the bit line BL 1 . In addition, a plurality of pillars  53 A and a plurality of pillars  53 B each coupled to the drive circuit  4  are formed. 
     Finally, as illustrated in  FIG. 15 , a plurality of beams  54 A are formed that each link the contact pillar  52 A and the pillar  53 A to each other, and a plurality of beams  54 B are formed that each link the contact pillar  52 B and the pillar  53 B to each other. 
     This completes the memory device  1 C. 
     [Workings and Effects of Memory Device  1 C] 
     The memory device  1 B allows the peripheral region PR and the memory cell region MR located at a level different therefrom to overlap each other, thus making it possible to utilize a space efficiently and thus to include more memory cells MC in a predetermined space. Thus, it becomes possible to achieve higher integration. Further, the resistance change element VR has substantially the same planar shape as that of the word line WL or the bit line BL immediately above the resistance change element VR, thus making it possible to simplify the manufacturing process. It is to noted that  FIG. 18A  illustrates a Y-Z cross-section along the word line WL, and  FIG. 18B  illustrates an X-Z cross-section along the bit line BL. 
     As illustrated in  FIG. 18A , each word line WL includes the peripheral regions PR at both ends in the Y-axis direction, and is coupled to the drive circuit  4  (not illustrated) by the contact pillars  51  each extending downward. In the memory device  1 C of the present embodiment, the word line WL has an overhang structure in which a size of the word line WL in the Y-axis direction is increased as the level becomes higher. In contrast, as illustrated in  FIG. 18B , the bit line BL has the stepped structure in which a size of the bit line BL in the X-axis direction is decreased as the level becomes higher. Thus, it becomes possible to collectively form the contact pillar  52  and so forth for each of the bit lines BL. 
     6. Application Example 
     Description is given next, with reference to  FIG. 19 , of a memory system including each of the memory devices  1 ,  1 A,  1 B, and  1 C (hereinafter, described collectively as the memory device  1 ) described in the foregoing respective first to third embodiments. The memory system illustrated in  FIG. 19  includes, besides the memory device  1 , a controller  7  and a host  8 . The controller  7  has, as a control section, a function of governing general operations of the memory device  1 . The host  8  is an external device that outputs a command to the controller  7 . 
     The memory device  1  includes the memory cell block MB, the drive circuit  4 , and an interface section  5 . The interface section  5  has functions of transmitting and receiving data to and from the controller  7 . The memory cell block MB refers to one integrated form of the plurality of memory cells MC illustrated in  FIG. 1 , etc. In the memory device  1 , a plurality of memory cell blocks MB are coupled to one drive circuit  4 . The plurality of memory cell blocks MB coupled to one drive circuit  4  is referred to, collectively, as a memory cell block array  6 . 
     For example, in the memory device  1  illustrated in  FIG. 1 , four memory cells are surely disposed in one columnar electrode BL (vertical wiring line selected by the GSL and the SL) that penetrates the memory cell units MU 1  to MU 4  in the Z-axis direction in a region that does not overlap the peripheral region (contact region) PR, i.e., in a region that overlaps the memory cell region MR 4 . In contrast, only one to three memory cells MC are disposed for the one columnar electrode BL in a region that overlaps any of the peripheral regions (contact regions) PR 1  to PR 4 . Accordingly, in the region that overlaps any of the peripheral regions (contact regions) PR 1  to PR 4 , there is generated an ineffective address where no memory cell MC is present depending on a combination of the selection lines, thus generating a discontinuous address region in a physical address space. 
     Therefore, in the present memory system, peripheral memory cells MC disposed in the region that overlaps any of the peripheral regions PR (PR 1  to PRn) are not used during a normal operation, but are used, as substitutions, in a case where, for example, access failure occurs to other memory cells MC. In order to perform such a substitution process, it is desirable for the controller  7  to include an address conversion table. The address conversion table is installed as a function. For example, when an address of a memory cell MC to be accessed is inputted, the address conversion table as a function returns an address of the substituted memory cell MC when the substitution process is performed, and returns zero when the substitution process is not performed. In this manner, by assigning the peripheral memory cell MC as an address to be used for the substitution process, it becomes possible to cause the host  8  to recognize the memory device as a continuous address region, thus allowing for easy handleability. 
     Further, in a case where the resistance change element VR is used as the memory cell MC, it is necessary to perform an initial process referred to as forming, depending on its characteristics, before initial writing after the production thereof. More specifically, as the forming, one or more of the following operations are performed. The operations include: (1) applying a higher voltage; (2) applying for a longer period of time; and (3) applying a plurality of pulses more continuously, than a pulse to be applied to the memory cell MC in a normal writing process. It is desirable that the peripheral memory cell MC to be used for the above-described substitution process be subjected to the forming at the time of the substitution. This is because there is a possibility that, selection of the plate-shaped electrode WL and the columnar electrode BL for access to any other memory cell instead of direct access to a memory cell to be used for the substitution process may cause a leak current to flow also to the memory cell to deteriorate characteristics as the memory cell. A memory cell not having been subjected to the forming, i.e., a memory cell in a state of not having been subjected to the forming even once after production is preferable because the deterioration is smaller than that of the memory cell having been subjected to the forming. 
     Further, upon formation of the plurality of memory cells MC in a normal thin-film process, the plurality of memory cells MC formed at a position close to the middle in a certain direction tends to exhibit more stable characteristics than those located at both ends. From this point of view, in the present memory system, instead of using the peripheral memory cells MC, use of other memory cells MC during the normal operation enables a more stable operation to be expected. 
     Although description has been given hereinabove referring to the embodiment, the disclosure is not limited to the foregoing embodiment and may be modified in a variety of ways. 
     Description has been given specifically referring to, for example, the configuration such as the memory device  1  and the memory system in the foregoing embodiments; however, all of the components are not necessarily included. Any other component may be further included. 
     Further, in the foregoing embodiment, etc., the resistance change element (resistance change memory) is used as the memory cell; however, the technology is not limited thereto. For example, other types of memories such as a phase-change memory (PCM), MRAM, and STTRAM may be used. 
     Further, the numbers of the respective components described in the foregoing embodiments, etc. are merely examples. Thus, the technology is not limited thereto, and may have any other number thereof. 
     It is to be noted that the effects described herein are merely examples, and are not limited thereto; the effects may further include other effects. Moreover, the technology may have the following configurations. 
     (1) 
     A memory device including 
     n-number of memory cell units that are provided on a substrate and stacked in order as a first memory cell unit to an n-th memory cell unit in a first direction, 
     the n-number of memory cell units each including 
     one or more first electrodes, 
     a plurality of second electrodes each provided to intersect the first electrode, 
     a plurality of memory cells provided at respective intersections of the first electrode and the plurality of second electrodes, and each coupled to both of the first electrode and the second electrode, and 
     one or more lead lines that are coupled to the first electrode to form one or more coupling parts, 
     the one or more coupling parts in an (m+1)-th memory cell unit of the memory cell units being located at a position where the one or more coupling parts and an m-th memory cell region overlap each other in the first direction, where m denotes a natural number equal to or smaller than n, the m-th memory cell region being surrounded by the plurality of memory cells in an m-th memory cell unit of the memory cell units. 
     (2) 
     The memory device according to (1), in which the coupling part in the (m+1)-th memory cell unit is located at a position where the coupling part and the plurality of memory cells in the m-th memory cell unit overlap each other in the first direction. 
     (3) 
     The memory device according to (1) or (2), in which an (m+1)-th memory cell region surrounded by the plurality of memory cells in the (m+1)-th memory cell unit is narrower than the m-th memory cell region. 
     (4) 
     The memory device according to any one of (1) to (3), in which the number of the plurality of memory cells in the (m+1)-th memory cell unit is smaller than the number of the plurality of memory cells in the m-th memory cell unit. 
     (5) 
     The memory device according to any one of (1) to (4), in which 
     the memory cell includes a resistance change element including a stacked 
     structure of an ion supply layer and an insulating layer, and the resistance change element is interposed between the first electrode and the second electrode. 
     (6) 
     The memory device according to any one of (1) to (5), further including a drive circuit coupled to the lead line. 
     (7) 
     The memory device according to any one of (1) to (6), in which 
     the first electrode includes a plate-shaped electrode that extends along a first surface that is orthogonal to the first direction, 
     the plurality of second electrodes include a plurality of columnar electrodes each stand from the plate-shaped electrode toward the substrate, and 
     the plate-shaped electrode in the (m+1)-th memory cell unit has an occupation area that is smaller than an occupation area of the plate-shaped electrode in the m-th memory cell unit. 
     (8) 
     The memory device according to any one of (1) to (6), in which 
     the first electrode includes a plurality of first linear electrodes and a plurality of second electrodes that each extend in a second direction along a first surface that is orthogonal to the first direction, and are arranged alternately in a third direction along the first surface, 
     the plurality of second electrodes include a plurality of columnar electrodes each interposed between the first linear electrode and the second linear electrode that are adjacent to each other, 
     the plurality of memory cells include a plurality of storage layers each interposed between corresponding one of the plurality of the columnar electrodes and corresponding one of each of the plurality of first linear electrodes and the plurality of second linear electrodes, the first linear electrodes and the second linear electrodes facing each other to interpose the columnar electrodes, and 
     the lead line includes a first contact pillar that forms a first coupling part as the coupling part through coupling to the first linear electrode, and a second contact pillar that forms a second coupling part as the coupling part through coupling to the second linear electrode. 
     (9) 
     The memory device according to (8), in which 
     the first linear electrode in the (m+1)-th memory cell unit has a size, in the second direction, that is smaller than a size, in the second direction, of the first linear electrode in the m-th memory cell unit, and 
     the second linear electrode in the (m+1)-th memory cell unit has a size, in the second direction, that is smaller than a size, in the second direction, of the second linear electrode in the m-th memory cell unit. 
     (10) 
     The memory device according to (8) or (9), in which 
     a plurality of the first contact pillars coupled to the respective first linear electrodes in the m-th memory cell unit are coupled in common to one of first beams, and 
     a plurality of the second contact pillars coupled to the respective second linear electrodes in the m-th memory cell unit are coupled in common to one of second beams. 
     (11) 
     The memory device according to (7), further including a plurality of selection lines that are arranged in a second direction along the first surface, and extend in a third direction orthogonal to the second direction along the first surface, the plurality of selection lines being each coupled to the plurality of second electrodes that are arranged in the third direction. 
     (12) 
     The memory device according to any one of (1) to (6), in which 
     the plurality of second electrodes, the plurality of memory cells, and the plurality of first electrodes are stacked in order from side of the substrate in the first direction, 
     the plurality of memory cells each have a stacked structure in which a resistance change element and a selection element are stacked in order on corresponding one of the plurality of second electrodes, and 
     the resistance change element has a planar shape that is substantially same as one of the plurality of first electrodes. 
     (13) 
     The memory device according to (12), in which 
     the plurality of first electrodes are disposed to each extend in a second direction along the first surface and to be arranged in a third direction orthogonal to the second direction, 
     the plurality of second electrodes are disposed to each extend in the third direction and to be arranged in the second direction, 
     a plurality of the selection elements are disposed to be arranged in both of the second direction and the third direction, and 
     the single resistance change element is coupled in common to the plurality of the selection elements that are arranged in one of the second direction and the third direction. 
     (14) 
     The memory device according to (12) or (13), in which 
     an (m+1)-th memory cell region surrounded by the plurality of memory cells in the (m+1)-th memory cell unit is narrower than the m-th memory cell region, and 
     the lead line includes a first contact pillar and a second contact pillar, the first contact pillar forming a first coupling part as the coupling part through coupling to the first electrode and extending to be away from the substrate, the second contact pillar forming a second coupling part as the coupling part through coupling to the second electrode and extending to be away from the substrate. 
     (15) 
     The memory device according to (14), further including: 
     a drive circuit provided between the substrate and a first memory cell unit of the memory cell units; 
     a first wiring line that couples an upper end of the first contact pillar and the drive circuit to each other; and 
     a second wiring line that couples an upper end of the second contact pillar and the drive circuit to each other. 
     (16) 
     The memory device according to (12) or (13), in which the lead line includes a first contact pillar and a second contact pillar, the first contact pillar forming a first coupling part as the coupling part through coupling to the first electrode and extending to be away from the substrate, the second contact pillar forming a second coupling part as the coupling part through coupling to the second electrode and extending toward the substrate. 
     (17) 
     The memory device according to (16), further including: 
     a drive circuit provided between the substrate and a first memory cell unit of the memory cell units; 
     a first wiring line that couples an upper end of the first contact pillar and the drive circuit to each other; and 
     a second wiring line that couples a lower end of the second contact pillar and the drive circuit to each other. 
     (18) 
     A memory system including: 
     a memory device; and 
     a controller that controls the memory device, 
     the memory device being provided with n-number of memory cell units that are provided on a substrate and stacked in order as a first memory cell unit to an n-th memory cell unit in a first direction, the n-number of memory cell units each including 
     one or more first electrodes, 
     a plurality of second electrodes each provided to intersect the first electrode, 
     a plurality of memory cells provided at respective intersections of the first electrode and the plurality of second electrodes, the plurality of memory cells each coupled to both of the first electrode and the second electrode, and 
     one or more lead lines that are coupled to the first electrode to form one or more coupling parts, the one or more coupling parts in an (m+1)-th memory cell unit of the memory cell units being located at a position where the one or more coupling parts and an m-th memory cell region overlap each other in the first direction, the m-th memory cell region being surrounded by the plurality of memory cells in an m-th memory cell unit of the memory cell units, where m denotes a natural number equal to or smaller than n. 
     (19) 
     The memory system according to (18), in which the memory cell provided in a peripheral region, of the m-th memory cell region, serves as a spare memory cell, the peripheral region being a region other than a region that is overlapped, in the first direction, by an (m+1)-th memory cell region surrounded by the plurality of memory cells in the (m+1)-th memory cell unit. 
     This application is based upon and claims priority from Japanese Patent Application No. 2015-117228 filed with the Japan Patent Office on Jun. 10, 2015, the entire contents of which are hereby incorporated by reference. 
     It should be understood by those skilled in the art that various modifications, combinations, sub-combinations, and alterations may occur depending on design requirements and other factors insofar as they are within the scope of the appended claims or the equivalents thereof