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

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.

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.