Semiconductor memory devices and methods for fabricating the same
A semiconductor memory device includes a substrate having a cell region and a peripheral region, a gate stack including a plurality of insulating layers and a plurality of gates alternately stacked on the cell region of the substrate, a stress buffer layer on the gate stack, a vertical channel that extends vertically through the gate stack and is electrically connected to the substrate, a memory layer wrapped around the vertical channel. A bit line electrically connected to the vertical channel may be provided on the gate stack. In a method of fabricating a semiconductor device, the buffer stress layer is formed directly on an upper insulating layer of a stack whose shape is altered to form the gate stack to inhibit warping of the substrate during fabrication of the device.
1. A semiconductor memory device comprising:
a substrate including a cell region and a peripheral region;
a gate stack including insulating layers and gates alternately stacked on and confined to the cell region of the substrate, at least one side of the gate stack having the form of a staircase;
a stress buffer layer on the gate stack;
a column, comprising a vertical channel, extending vertically through the stress buffer layer and the gate stack, the vertical channel being electrically connected to the substrate;
a memory layer surrounding the vertical channel; and
a bit line on the gate stack and electrically connected to the vertical channel.
2. The device of claim 1 , wherein the stress buffer layer covers the uppermost gate of the gate stack.
3. The device of claim 1 , wherein the stress buffer layer has the shape of a plate, extends across the cell and peripheral regions, and covers the uppermost gate of the gate stack.
4. The device of claim 1 , wherein at least one portion of the stress buffer layer has the shape of a staircase, and the at least one portion of the stress buffer layer covers the at least one side of the gate stack.
5. The device of claim 4 , wherein the stress buffer layer has a portion covering the uppermost gate of the gate stack.
6. The device of claim 1 , wherein the stress buffer layer has:
a first portion having the shape of a staircase on the cell region and covering the at least one side of the gate stack; and
a second portion having the shape of a plate and covering the peripheral region of the substrate, the second portion of the buffer layer extending contiguously from the first portion of the buffer layer.
7. The device of claim 6 , wherein the buffer layer also has a portion covering the uppermost gate of the gate stack.
8. The device of claim 1 , wherein the column comprises a pillar of semiconductor material.
9. The device of claim 1 , wherein the column comprises a drain within the stress buffer layer.
10. The device of claim 1 , wherein the memory layer extends vertically through the stress buffer layer.
11. A semiconductor memory device comprising:
a substrate including a cell region and a peripheral region;
a gate stack including insulating layers and gates alternately stacked on and confined to the cell region of the substrate, at least one side of the gate stack having the form of a staircase;
a stress buffer layer on the gate stack;
a vertical channel extending vertically through the gate stack and electrically connected to the substrate;
a memory layer surrounding the vertical channel; and
a bit line on the gate stack and electrically connected to the vertical channel, and
wherein the stress buffer layer has the shape of a plate, extends across the cell and peripheral regions, and covers the uppermost gate of the gate stack.