Semiconductor device and method for fabricating the same
A semiconductor device including highly integrated memory cells and a method for fabricating the same in which the method includes: forming a semiconductor layer pattern over a lower structure; forming a gate dielectric layer covering the semiconductor layer pattern; forming a conductive layer surrounding the semiconductor layer pattern over the gate dielectric layer; forming a pair of horizontal conductive layer patterns respectively disposed over an upper surface and a lower surface of the semiconductor layer pattern by selectively etching the conductive layer; forming a horizontal layer having a side portion between the pair of horizontal conductive layer patterns by selectively recessing the semiconductor layer pattern; and forming a pair of horizontal conductive lines respectively disposed over an upper surface and a lower surface of the horizontal layer by recessing the pair of horizontal conductive layer patterns.
1 . A method for fabricating a semiconductor device, the method comprising:
forming a semiconductor layer pattern over a lower structure;
forming a gate dielectric layer covering the semiconductor layer pattern;
forming a conductive layer surrounding the semiconductor layer pattern over the gate dielectric layer;
forming a pair of horizontal conductive layer patterns respectively disposed over an upper surface and a lower surface of the semiconductor layer pattern by selectively etching the conductive layer;
forming a horizontal layer having a side portion between the pair of horizontal conductive layer patterns by selectively recessing the semiconductor layer pattern; and
forming a pair of horizontal conductive lines respectively disposed over an upper surface and a lower surface of the horizontal layer by recessing the pair of horizontal conductive layer patterns.
2 . The method of claim 1 , wherein the forming of the semiconductor layer pattern comprises:
sequentially forming a first sacrificial layer structure, a semiconductor layer, and a second sacrificial layer structure in order to form a stack body over the lower structure;
forming a first opening in the stack body;
removing the first sacrificial layer structure and the second sacrificial layer structure through the first opening; and
recessing the semiconductor layer in order to form the semiconductor layer pattern.
3 . The method of claim 2 , wherein the first and second sacrificial layer structures each include a stack of a first silicon germanium layer, a first single crystal silicon layer, and a second silicon germanium layer, and
the semiconductor layer includes a second single crystal silicon layer thicker than the first single crystal silicon layer.
4 . The method of claim 1 , wherein the upper surface and the lower surface of the semiconductor layer pattern each include a flat surface.
5 . The method of claim 1 , wherein the gate dielectric layer covers the upper surface and the lower surface of the semiconductor layer pattern.
6 . The method of claim 1 , wherein the gate dielectric layer is formed by a deposition process of silicon oxide or a surface oxide process of the semiconductor layer pattern.
7 . The method of claim 1 , further comprising:
forming a vertical conductive line coupled to one end of the horizontal layer; and
forming a data storage element coupled to the other end of the horizontal layer.
8 . The method of claim 1 , wherein the semiconductor layer pattern includes a single crystal silicon layer.
9 . The method of claim 1 , wherein the conductive layer includes polysilicon, metal, metal nitride, or a combination thereof.
10 . The method of claim 1 , wherein the forming of the conductive layer comprises:
forming a metal-base layer surrounding the semiconductor layer pattern over the gate dielectric layer.
11 . The method of claim 1 , wherein the forming of the pair of horizontal conductive lines comprises:
forming a pair of first work function electrodes respectively disposed over the upper surface and the lower surface of the semiconductor layer pattern over the gate dielectric layer;
forming a pair of second work function electrodes over one side of the first work function electrodes; and
forming a pair of third work function electrodes over the other sides of the first work function electrodes.
12 . The method of claim 11 , wherein the second and third work function electrodes each include a low work function material, and the first work function electrode includes a high work function material.
13 . The method of claim 11 , wherein the second and third work function electrodes each include N-doped polysilicon, and the first work function electrode includes tungsten.
14 . The method of claim 11 , further comprising:
forming a first barrier layer between the first work function electrode and the second work function electrode; and
forming a second barrier layer between the first work function electrode and the third work function electrode.
15 . The method of claim 14 , wherein the first and second barrier layers each include metal nitride.