A method of making a monolithic, three dimensional NAND string, includes forming a semiconductor active region of a first memory cell over a semiconductor active region of a second memory cell. The semiconductor active region of the first memory cell is a first pillar having a square or rectangular cross section when viewed from above, the first pillar being a first conductivity type semiconductor region located between second conductivity type semiconductor regions. The semiconductor active region of the second memory cell is a second pillar having a square or rectangular cross section when viewed from above, the second pillar located under the first pillar, the second pillar being a first conductivity type semiconductor region located between second conductivity type semiconductor regions. One second conductivity type semiconductor region in the first pillar contacts one second conductivity type semiconductor region in the second pillar.