Three-dimensional nand memory device and method of forming the same

Abstract

In a method for fabricating a semiconductor device, an initial stack is formed. The initial stack is formed of sacrificial layers and insulating layers that are alternatingly disposed over a substrate, and includes a first connection region, a first array region, and a second connection region that are disposed sequentially. A first initial staircase is formed in the first connection region and formed in a first group of sacrificial layers and insulating layers. A first top select gate staircase is formed in the second connection region, and formed in a second group of sacrificial layers and insulating layers. An etching process is subsequently performed in the first connection region to shift the first initial staircase toward the substrate along a vertical direction perpendicular to the substrate so as to form a first bottom select gate staircase.