Semiconductor device having buried bit lines and method for fabricating the same

1. A method for fabricating a semiconductor device, the method comprising:

etching a substrate to form a plurality of bodies, having sidewalls, separated by a plurality of trenches, where each trench, of the plurality of trenches is defined by a pair of sidewalls of corresponding ones of the plurality of bodies;

forming, in the substrate under each trench, of the plurality of trenches, silicidation preventing regions; and

performing a silicidation process on the sidewalls of the plurality of bodies to form buried bit lines in each body, of the plurality of bodies, where lower surfaces of the buried bit lines are substantially co-planar with bottoms of the plurality of trenches.

2. The method of claim 1 , wherein the silicidation preventing regions are to prevent metal silicides from being formed in the substrate during a silicidation process.

3. The method of claim 1 , further comprising:

forming punch-through preventing regions in the substrate under the silicidation preventing regions before forming the buried bit lines.

4. The method of claim 1 , wherein forming the buried bit lines further comprises:

forming a passivation layer on the pair of sidewalls before forming the silicidation preventing regions;

removing portions of the passivation layer that are adjacent to a bottom of each trench, of the plurality of trenches, after forming the silicidation preventing regions to define open parts that expose the pair of sidewalls;

forming a metal-containing layer over the pairs of sidewalls exposed by the open parts;

forming a metal silicide layer in each body, of the plurality of bodies via annealing; and

removing any remaining metal-containing layer.

5. The method of claim 1 , wherein the buried bit lines comprise a cobalt silicide.

6. A method for fabricating a semiconductor device, the method comprising:

etching a silicon-containing substrate to form a plurality of bodies, having sidewalls, separated by a plurality of trenches, wherein each trench, of the plurality of trenches is defined by a pair of sidewalls of corresponding ones of the plurality of bodies;

forming a passivation layer on the pairs of sidewalls;

forming silicidation preventing regions in the substrate under the trenches;

etching the passivation layer to define open parts that are substantially co-planar with bottoms of the plurality of trenches and that expose the pair of sidewalls;

forming a metal-containing layer over the pairs of sidewalls exposed by the open parts;

forming a metal silicide layer through a full thickness of each body, of plurality of bodies by silicidating a portion of each body, of the plurality of bodies, that is exposed by the open parts;

removing any remaining metal-containing layer; and

forming an interlayer dielectric layer to fill spaces between the plurality of bodies.

7. The method of claim 6 , further comprising:

forming punch-through preventing regions in the substrate under the silicidation preventing regions before etching the passivation layer to define the open parts.

8. The method of claim 6 , where forming the passivation layer comprises:

forming a first passivation layer over the pairs of sidewalls that define the plurality of trenches and over a surface of the silicon-containing substrate that defines bottoms of the plurality of trenches;

forming a sacrificial layer over the first passivation layer to partially fill each trench of the plurality of trenches;

forming a second passivation layer over the first passivation layer on the pairs of side ails;

removing the sacrificial layer; and

removing portions of the first passivation layer that are formed over the surface of the silicon-containing substrate that defines bottoms of the plurality of trenches.

9. The method of claim 8 , wherein etching the passivation layer to define the open parts further comprises:

removing exposed portions of the first passivation layer using the second passivation layer as an etch mask.

10. The method of claim 7 , wherein forming the silicidation preventing regions further comprises:

ion-implanting fluorine into the substrate.

11. The method of claim 10 , wherein the silicidation preventing regions comprise silicon fluoride regions.

12. The method of claim 6 , wherein the metal silicide layer comprises a cobalt silicide layer.

13. A method for fabricating a semiconductor device, comprising:

etching a substrate to form a plurality of bodies, having sidewalls, separated by a plurality of trenches, wherein each trench, of the plurality of trenches is defined by a pair of sidewalls of corresponding ones of the plurality of bodies;

forming silicidation preventing regions in the substrate under each trench of the plurality of trenches;

performing silicidation on the pairs of sidewalls to form buried bit lines in each body, of the plurality of bodies, wherein lower surfaces of the buried bit lines are substantially aligned with bottoms of the plurality of trenches; and

etching the plurality of to form a plurality of pillars that are to connect with corresponding capacitors and include channel regions for vertical channel transistors.

14. The method of claim 13 , the method further comprising:

forming punch-through preventing regions in the substrate under the silicidation preventing regions before the forming the buried bit lines.

15. The method of claim 13 , wherein forming the buried bit lines comprises:

forming a passivation layer on the pairs of sidewalls before forming the silicidation preventing regions;

removing portions of the passivation layer which are adjacent to a bottom of each trench, of the plurality of trenches, after forming the silicidation preventing regions to define open parts that expose the pair of sidewalls;

forming a metal-containing layer over the pair of sidewalls exposed by the open parts;

forming a metal silicide layer in each body, of the plurality of bodies via annealing; and

removing any remaining metal-containing layer.

16. The method of claim 1 wherein the buried bit lines comprise a cobalt silicide.

17. A semiconductor device comprising:

a substrate;

a plurality of bodies defined in the substrate, where the plurality of bodies are separated from one another by trenches that are defined by sidewalls of the plurality of bodies and by a surface of the substrate;

buried bit lines, made of a metal silicide, formed in each of the plurality of bodies, where a bottom surface of each of the buried bit lines is substantially co-planar with surfaces defining bottoms of the trenches; and

silicidation preventing regions formed in the substrate under the trenches, where the silicidation preventing regions are to prevent metal silicides from being formed in the substrate during a silicidation process.

18. The semiconductor device of claim 17 , where the substrate comprises a silicon-containing substance, and the silicidation preventing regions comprise silicon-fluoride regions.

19. The semiconductor device of claim 17 , further comprising:

punch-through preventing regions formed in the substrate under the silicidation preventing regions.

20. The semiconductor device of claim 17 , wherein the metal silicide comprises a cobalt silicide.

21. The semiconductor device of claim 17 , further comprising:

vertical channel transistors, including pillars that are formed over each of the plurality of bodies; and

capacitors formed to be connected to the pillars.