3D memory device
A 3D memory device, comprising a plurality of rows of strings of memory cells, each row of strings of memory cells comprising an array of strings of memory cells extending along a first direction, the rows following one another along a second direction. Each string of memory cells comprises a stack of memory cells, and the strings of memory cells of the stack extend in a third direction from a first end to a second end. A source region is provided at the second end of the strings of memory cells. Consecutive rows of strings of memory cells along the second direction are spaced apart from each other of a pitch. Between pairs of strings of a row of memory cells along the second direction there is formed a slit extending in the third direction from the first end down to the source region. The slit has dimension, along the second direction, smaller than, equal to or greater than the pitch, sufficient to the formation, in the slit, of an electrical contact to the source region.
1. A method of making a three-dimensional, 3D, memory device comprising:
forming a plurality of rows of strings of memory cells, each row of strings of memory cells comprising an alignment of strings of memory cells extending along a first direction, said rows following one another along a second direction, wherein each string of memory cells comprises a stack of memory cells, said strings of memory cells of the stack extending along a third direction from a first end to a second end, wherein rows of strings of memory cells consecutive along said second direction are spaced apart from each other of a pitch;
forming a source region at the second end of the strings of memory cells;
forming, between pairs of said rows of strings of memory cells consecutive along said second direction, a slit extending in said third direction from said first end to said source region, wherein said slit has size, along said second direction, less, equal or greater than said pitch sufficient for the formation, in said slit, of an electrical contact to the source region;
forming said electrical contact to the source region;
wherein said slit has size, along said second direction, substantially equal to said pitch of the rows of strings of memory cells consecutive along said second direction.
2. The method of claim 1 , wherein:
said forming a plurality of rows of strings of memory cells comprises forming strings of memory cells having a size along said second direction;
said forming, between pairs of said rows of strings of memory cells consecutive along said second direction, a slit comprises slicing and removing portions of the strings of memory cells, said sliced and removed portions extending along said third direction from said first end to said source region and having length along said second direction less, equal or greater than half of said size of the strings of memory cells in said second direction.
3. The method of claim 2 , wherein:
said sliced and removed portions extend along said second direction of a length substantially equal to said pitch of consecutive rows of memory cell strings which are consecutive along said second direction.
4. The method of claim 1 , wherein:
said forming a plurality of rows of strings of memory cells comprises realizing substantially cylindrical strings of memory cells with an axis along said third direction, and
said forming a slit between pairs of said consecutive rows of strings of memory cells which are consecutive along said second direction creates strings of memory cells with a shape of a portion of a cylinder, preferably a semi-cylindrical shape.