NAND-type flash memory device and method of forming the same

摘要

A NAND-type flash memory device for preventing punchthrough and a method for forming the same are provided. The NAND-type flash memory device includes a string selection transistor, a plurality of cell memory transistors, and a ground selection transistor being sequentially connected in series. The device further includes a bitline contact connected to a drain region of the string selection transistor, and a common source line connected to a source region of the ground selection transistor. Impurities are heavily doped to a drain-to-channel interface in the string selection transistor and a channel-to-source interface in the ground selection transistor, forming pockets for preventing punchthrough. The pockets are preferably formed using a tilted ion implantation using the vertical gate structures as masks.