A semiconductor memory device and a method for fabricating the same are provided. The semiconductor memory device includes a plurality of gate stacks separated by a plurality of slit structures, and each of the gate stacks includes: a first stack including three or more first conductive patterns spaced apart from one another at substantially a same level; a second stack formed on the first stack and including second conductive patterns and interlayer dielectric layers alternately stacked; and a plurality of channel structures penetrating the second stack and the first stack.