Patent ID: 8580639

Claim:
A method of making a monolithic three dimensional NAND string, comprising: forming a stack of alternating layers of a first layer and a second layer, wherein the first layer comprises a first sacrificial sub-layer, a second sacrificial sub-layer and a third sacrificial sub-layer located between the first sacrificial sub-layer and the second sacrificial sub-layer; etching the stack to form at least one opening in the stack; selectively etching the third sacrificial sub-layer to form first recesses; forming a plurality of discrete charge storage segments separated from each other in the first recesses; forming a tunnel dielectric over a side wall of the discrete charge storage segments exposed in the at least one opening; forming a semiconductor channel in the at least one opening; etching the stack to expose a back side of the stack; removing the first sacrificial sub-layer, the second sacrificial sub-layer and the third sacrificial sub-layer to form clam-shaped openings such that the plurality of discrete charge storage segments are exposed in the clam-shaped openings; forming a plurality of clam-shaped blocking dielectric segments in the clam-shaped openings over the plurality of discrete charge storage segments; and forming a plurality of clam-shaped control gate electrodes in the clam-shaped openings over the plurality of the clam-shaped blocking dielectric segments; wherein: the second layer comprises an insulating layer; and the third sacrificial sub-layer comprises a sacrificial material different from the first sacrificial sub-layer, the second sacrificial sub-layer, and the second layer.