Three dimensional semiconductor memory including pillars having joint portions between columnar sections

Abstract

According to one embodiment, a semiconductor memory includes a plurality of conductors stacked with insulators being interposed therebetween and a pillar through the plurality of conductors. The pillar includes a first columnar section, a second columnar section, and a joint portion between the first columnar section and the second columnar section. The pillar comprises portions that cross the respective conductors and that each function as part of a transistor. The plurality of conductors include a first conductor. The first conductor is closest to the joint portion among the plurality of conductors through the second columnar section, and includes a bending portion formed along the joint portion.

What is claimed is: 
     
         1 . A semiconductor memory comprising:
 a plurality of conductors stacked in a first direction with insulators being interposed therebetween; and   a pillar extending in the first direction through the plurality of conductors, the pillar including a first columnar section, a second columnar section above the first columnar section, and a joint portion between the first columnar section and the second columnar section, and the pillar comprising portions that cross the respective conductors, the portions respectively functioning as part of a transistor, wherein   the plurality of conductors include a first conductor that is closest to the joint portion among the plurality of conductors through the second columnar section, the first conductor includes a first portion surrounding the pillar, a second portion surrounding the first portion, and a third portion surrounding the second portion when viewed from the first direction, a bottom surface of the second portion has the same level in the first direction as a bottom surface of the third portion, and a bottom surface of the first portion is upper than the bottom surfaces of the second and third portions,   the plurality of conductors include a third conductor that is closest to the joint portion among the plurality of conductors through the first columnar section,   a first distance is smaller than a second distance,   the first distance is a distance, in a stacking direction of the plurality of conductors, between adjacent conductors among the plurality of conductors through the second columnar section, and   the second distance is a distance in the stacking direction between the first conductor and the third conductor.   
     
     
         2 . The memory of  claim 1 , wherein the joint portion abuts each of the first columnar section and the second columnar section. 
     
     
         3 . The memory of  claim 2 , wherein an outer diameter of the joint portion in a cross-section area parallel to a surface of a substrate, is larger than an outer diameter of the second columnar section in a cross-section area parallel to the surface of the substrate and including a boundary portion between the second columnar section and the joint portion. 
     
     
         4 . The memory of  claim 3 , wherein the outer diameter of the joint portion is larger than an outer diameter of the first columnar section in a cross-section area parallel to the substrate and including a boundary portion between the first columnar section and the joint portion. 
     
     
         5 . The memory of  claim 3 , wherein a distance, in the first direction between the bottom surface of the first portion and the bottom surface of the third portion is smaller than a thickness of the first conductor in the first direction. 
     
     
         6 . The memory of  claim 5 , wherein the distance is equal to or smaller than a half of the thickness. 
     
     
         7 . The memory of  claim 1 , wherein the plurality of conductors include a second conductor that is second closest to the joint portion among the plurality of conductors through the second columnar section, and the second conductor includes a portion bending indirectly along the joint portion. 
     
     
         8 . The memory of  claim 1 , wherein a transistor provided in a portion where the first conductor crosses the second columnar section is not used for storing data. 
     
     
         9 . The memory of  claim 1 , wherein the plurality of conductors include a third conductor that is closest to the joint portion among the plurality of conductors through the first columnar section,
 a first distance is smaller than a second distance,   the first distance is a distance, in a stacking direction of the plurality of conductors, between adjacent conductors among the plurality of conductors through the second columnar section, and   the second distance is a distance in the stacking direction between the first conductor and the third conductor.   
     
     
         10 . The memory of claim  9   1 , wherein the third conductor has no portion bending along the joint portion. 
     
     
         11 . The memory of claim  9   1 , wherein a transistor provided in a portion where the third conductor crosses the first columnar section is not used for storing data. 
     
     
         12 . A semiconductor memory comprising:
 a plurality of conductors stacked in a first direction with insulators being interposed therebetween; and   a pillar extending in the first direction through the plurality of conductors, the pillar including a first columnar section and a second columnar section on the first columnar section, and the pillar comprising portions that cross the respective conductors, the portions respectively functioning as part of a transistor,   wherein the plurality of conductors include a first conductor that is closest to the first columnar section among the plurality of conductors through the second columnar section, the first conductor includes a first portion surrounding the pillar, a second portion surrounding the first portion, and a third portion surrounding the second portion when viewed from the first direction, a bottom surface of the second portion has the same level in the first direction as a bottom surface of the third portion, and a bottom surface of the first portion is upper than the bottom surfaces of the second and third portions, and   wherein a transistor provided in a portion where the first conductor crosses the second columnar section is not used for storing data.   
     
     
         13 . The memory of  claim 12 , wherein, in a boundary portion between the first columnar section and the second columnar section, an outer diameter of the first columnar section in a cross-section area parallel to a surface of a substrate is larger than an outer diameter of the second columnar section in a cross-section area parallel to the surface of the substrate. 
     
     
         14 . The memory of  claim 13 , wherein a distance, in the first direction between the bottom surface of the first portion and the bottom surface of the third portion is smaller than a thickness of the first conductor in the first direction. 
     
     
         15 . The memory of  claim 14 , wherein the distance is equal to or smaller than a half of the thickness. 
     
     
         16 . The memory of  claim 12 , wherein the plurality of conductors include a second conductor that is second closest to the first columnar section among the plurality of conductors through the second columnar section, and the second conductor includes a portion bending indirectly along the first columnar section. 
     
     
         17 . The memory of  claim 12 , wherein a transistor provided in a portion where the first conductor crosses the second columnar section is not used for storing data. 
     
     
         18 . The memory of  claim 12 , wherein the plurality of conductors include a third conductor that is closest to the second columnar section among the plurality of conductors through the first columnar section,
 a first distance is smaller than a second distance,   the first distance is a distance, in a stacking direction of the plurality of conductors, between adjacent conductors among the plurality of conductors through the second columnar section,   the second distance is a distance in the stacking direction between the first conductor and the third conductor.   
     
     
         19 . The memory of  claim 18 , wherein the third conductor has no portion bending along the joint portion. 
     
     
         20 . The memory of  claim 18 , wherein a transistor provided in a portion where the third conductor crosses the first columnar section is not used for storing data. 
     
     
       21. A semiconductor memory comprising:
 a first conductor;   a plurality of second conductors provided above the first conductor and stacked in a first direction with insulators interposed therebetween;   a plurality of bit lines provided above the plurality of second conductors; and   a plurality of pillars each passing in the first direction through the plurality of second conductors and each electrically connecting the first conductor to a corresponding one of the plurality of bit lines, the plurality of pillars each including a first columnar section and a second columnar section on the first columnar section, and the plurality of pillars each comprising portions that cross the respective second conductors, the portions respectively functioning as part of a transistor,   wherein the plurality of second conductors includes a third conductor and a fourth conductor that are a lowermost two in the first direction of the plurality of second conductors passing through the second columnar section,   the third conductor has a first thickness which is defined as a maximum thickness in the first direction in a first region between two of the plurality of pillars,   the fourth conductor has a second thickness which is defined as a maximum thickness in the first direction in the first region,   the plurality of second conductors includes a fifth conductor that is an uppermost one in the first direction of the plurality of second conductors through the first columnar section,   the fifth conductor has a third thickness in the first direction defined as a maximum thickness in the first region, and   the first thickness and the second thickness are respectively greater than the third thickness.   
     
     
       22. The memory of  claim 21 , wherein,
 a width in a second direction crossing the first direction of a portion of the first columnar section facing the fifth conductor is greater than a width in the second direction of a portion of the second columnar section facing the third conductor.   
     
     
       23. The memory of  claim 21 , wherein,
 the plurality of pillars each further includes one or more columnar sections in addition to the first columnar section and the second columnar section.   
     
     
       24. The memory of  claim 21 , wherein,
 the plurality of conductors further includes a sixth conductor that comprises with the third conductor and the fourth conductor a lowermost three in the first direction of the plurality of second conductors passing through the second columnar section,   the sixth conductor has a fourth thickness which is defined as maximum thickness in the first direction in the first region,   the fourth thickness is greater than the third thickness.   
     
     
       25. The memory of  claim 21 , wherein,
 the third conductor includes a first portion surrounding one of the pillars, a second portion surrounding the first portion, and a third portion surrounding the second portion when viewed from the first direction, a bottom surface of the second portion has the same level in the first direction as a bottom surface of the third portion, and a bottom surface of the first portion is upper than the bottom surfaces of the second and third portions.   
     
     
       26. The memory of  claim 25 , wherein, in a boundary portion between the first columnar section and the second columnar section, an outer diameter of the first columnar section in a cross-section area parallel to a surface of a substrate is larger than an outer diameter of the second columnar section in a cross-section area parallel to the surface of the substrate. 
     
     
       27. The memory of  claim 26 , wherein a distance, in the first direction between the bottom surface of the first portion and the bottom surface of the third portion is smaller than a thickness of the third conductor in the first direction. 
     
     
       28. The memory of  claim 27 , wherein the distance is equal to or smaller than a half of the thickness. 
     
     
       29. The memory of  claim 25 , wherein the fourth conductor includes a portion bending indirectly along the first columnar section. 
     
     
       30. The memory of  claim 25 , wherein a transistor provided in a portion where the third conductor crosses the second columnar section is not used for storing data. 
     
     
       31. The memory of  claim 25 , wherein
 a first distance is smaller than a second distance,   the first distance is a distance, in the first direction, between adjacent second conductors among the plurality of second conductors through the second columnar section,   the second distance is a distance, in the first direction, between the third conductor and the fifth conductor.   
     
     
       32. The memory of  claim 31 , wherein the fifth conductor has no portion bending along the joint portion. 
     
     
       33. The memory of  claim 31 , wherein a transistor provided in a portion where the fifth conductor crosses the first columnar section is not used for storing data.