Patent ID: 6940109

Claim:
A monolithic three dimensional array of field effect transistors, comprising: (a) a substrate; (b) a plurality of first rails disposed at a first height relative to the substrate in a first direction, wherein each of the plurality of first rails comprises a first-rail heavily doped semiconductor layer of a first conductivity type; (c) a plurality of second rails disposed at a second height different from the first height, and in a second direction different from the first direction, wherein each of the plurality of second rails comprises: a second-rail lightly doped semiconductor channel layer of a second conductivity type located in contact with the first rails; a second-rail heavily doped semiconductor layer of the first conductivity type; a second-rail gate insulating layer between and in contact with the second-rail channel layer and the second-rail heavily doped semiconductor layer of the first conductivity type; and a second-rail heavily doped semiconductor layer of the second conductivity type electrically connected to the second-rail heavily doped semiconductor layer of the first conductivity type by a second-rail metal or metal silicide layer; (d) a plurality of third rails disposed in the first direction at a third height relative to the substrate, wherein each of the plurality of third rails comprises: a third-rail lightly doped semiconductor channel layer of the first conductivity type located in contact with the second-rail heavily doped semiconductor layer of the second conductivity type in the second rails; a third-rail heavily doped semiconductor layer of the second conductivity type; a third-rail heavily doped semiconductor layer of the first conductivity type electrically connected to the third-rail heavily doped semiconductor layer of the second conductivity type by a third-rail metal or metal silicide layer; and a third-rail gate insulating layer between and in contact with the third-rail channel layer and the third-rail heavily doped semiconductor layer of the second conductivity type.