Patent ID: 8461641

Claim:
A method of making a monolithic three dimensional NAND string, comprising: forming at least one sacrificial feature over a substrate; forming a stack of alternating layers of a first material and a second material over the at least one sacrificial feature, wherein the first material comprises a conductive or semiconductor control gate material; forming a cut area in the stack to separate the control gate material in a direction substantially perpendicular to a major surface of the substrate, wherein the cut area extends in a first direction substantially parallel to the major surface of the substrate and in a second direction substantially parallel to the major surface of the substrate, wherein the first direction is perpendicular to the second direction; etching the stack to form at least two openings in the stack; forming a blocking dielectric in the at least two openings; forming a charge storage region in the at least two openings over the blocking dielectric; removing the at least one sacrificial feature to form a hollow region extending substantially parallel to a major surface of the substrate which connects the at least two openings to form a hollow U-shaped pipe space comprising the first and the second openings extending substantially perpendicular to the major surface of the substrate connected by the hollow region; forming a tunnel dielectric over a side wall of the charge storage region exposed in the at least two openings; and forming a semiconductor channel in the hollow U-shaped pipe space.