Patent ID: 8227306

Claim:
A method of forming a multiple-layered memory device, comprising: providing a first memory device layer comprising: providing a first substrate including a first memory cell region, the first substrate comprising a semiconducting material doped with impurity of a first type; providing a first well in an upper region of the first memory cell region, the first well comprising a semiconducting material doped with impurity of a second type opposite the first type; and providing a second well in the first well, the second well comprising a semiconducting material doped with impurity of the first type, the second well of defining a first active region of the first substrate; and providing multiple first cell strings arranged on the first substrate in the first active region; and providing a second memory device layer on the first memory device layer comprising: providing a second substrate including a second memory cell region, the second substrate including only a single well in the second memory cell region, the single well of the second memory cell region comprising a semiconducting material doped with impurity of one of the first type and second type, the single well defining a second active region in the second memory cell region of the second substrate; and providing multiple second cell strings arranged on the second substrate in the second active region.