Semiconductor device including fin structures disposed over buffer structures and manufacturing method thereof

1. A method for manufacturing a semiconductor device, comprising:

forming a buffer structure over a substrate, the buffer structure having a fin-shape and extending along a first direction, the buffer structure having a different lattice constant than the substrate; and

after forming the fin-shaped buffer structure, forming a fin structure over an upper surface of the fin-shaped buffer structure,

wherein a width of the buffer structure along a second direction perpendicular to the first direction is greater than a width of the fin structure along the second direction measured at an interface between the buffer structure and the fin structure, the upper surface of the buffer structure being in contact with a bottom of the fin structure at the interface.

2. The method of claim 1 , wherein the forming a buffer structure comprises:

forming a first insulating layer over the substrate;

patterning the first insulating layer to form a first opening extending in the first direction such that an upper surface of the substrate is exposed in the first opening; and

forming a first semiconductor material in the first opening.

3. The method of claim 1 , wherein the forming a buffer structure comprises:

forming a dummy fin structure over the substrate;

forming a side wall spacer over a side surface of the dummy fin structure;

after forming the side wall spacer, forming a cover layer on an upper surface of the dummy fin structure and an upper surface of the substrate;

removing the side wall spacer after forming the cover layer so as to expose at least the side surface of the dummy fin structure;

forming a first semiconductor layer at least on the exposed side surface of the dummy fin structure; and

removing an upper portion of the formed first semiconductor layer.

4. The method of claim 3 , wherein:

in the removing the side wall spacer, a part of the substrate which has been covered by a bottom of the side wall spacer is also exposed, and

in the forming the first semiconductor layer, the first semiconductor layer is also formed on the exposed part of the substrate.

5. The method of claim 3 , wherein the side wall spacer and the cover layer are made of different materials.

6. The method of claim 5 , wherein the side wall spacer includes silicon nitride and the cover layer includes silicon oxide.

7. The method of claim 3 , wherein:

the removing an upper portion of the formed first semiconductor layer comprises forming a first insulating layer over the substrate so that the dummy fin structure and the first semiconductor layer are embedded in the first insulating layer, and

upper portion of the first insulating layer, the dummy fin structure and the formed first semiconductor layer are removed.

8. The method of claim 7 , further comprising, after removing the upper portion of the first insulating layer, the dummy fin structure and the formed first semiconductor layer:

removing the dummy fin structure to form a space; and

forming an additional insulating layer in the space.

9. The method of claim 1 , wherein the forming a fin structure comprises:

forming a second insulating layer over the buffer structure;

patterning the second insulating layer to form a second opening, the second opening overlapping the buffer structure;

forming a second semiconductor layer in the second opening.

10. The method of claim 9 , wherein before forming the second semiconductor layer, a third semiconductor layer is formed in the second opening.

11. The method of claim 1 , wherein:

the forming the fin structure include forming a lower part of the fin structure and forming an upper part of the fin structure on the lower part, and

a material of the lower part is different from a material of the upper part.

12. A method for manufacturing a semiconductor device, comprising:

forming buffer structures over a substrate, the buffer structures having a fin-shape and extending along a first direction and arranged in parallel with each other in a second direction crossing the first direction, the buffer structures having a different lattice constant than the substrate; and

after forming the fin-shaped buffer structures, forming a fin structure over an upper surface of a corresponding one of the fin-shaped buffer structures,

wherein a width of each of the buffer structures along the second direction is greater than a width of the fin structure along the second direction measured at an interface between the buffer structure and the fin structure, the upper surface of the buffer structure being in contact with a bottom of the fin structure at the interface.

13. The method of claim 12 , wherein the forming plural buffer structures comprises:

forming a first insulating layer over the substrate;

patterning the first insulating layer to form first openings in extending the first direction such that an upper surface of the substrate is exposed in the first openings; and

forming a first semiconductor material in the first openings.

14. The method of claim 12 , wherein the forming buffer structures comprises:

forming dummy fin structures over the substrate;

forming side wall spacers over side surfaces of the dummy fin structures;

after forming the side wall spacers, forming cover layers on upper surfaces of the dummy fin structures and an upper surface of the substrate;

removing the side wall spacers after forming the cover layers so as to expose the side surfaces of the dummy fin structures and a portion of the substrate which has been covered by bottoms of the side wall spacers;

forming first semiconductor layers at least on the exposed side surfaces of the dummy fin structures and the exposed portion of the substrate; and

removing upper portions of the formed first semiconductor layers.

15. The method of claim 14 , wherein:

the removing upper portions of the formed first semiconductor layers comprises forming a first insulating layer over the substrate so that the dummy fin structures and the first semiconductor layers are embedded in the first insulating layer, and

upper portion of the first insulating layer, the dummy fin structures and the formed first semiconductor layers are removed.

16. The method of claim 15 , further comprising, after removing the upper portion of the first insulating layer, the dummy fin structures and the formed first semiconductor layers:

removing the dummy fin structures to form spaces; and

forming additional insulating layers in the spaces.

17. The method of claim 12 , wherein the forming a fin structure comprises:

forming a second insulating layer over the buffer structures;

patterning the second insulating layer to form a second opening, the second opening overlapping one of the buffer structures;

forming a second semiconductor layer in the second opening.

18. The method of claim 17 , wherein before forming the second semiconductor layer, a third semiconductor layer is formed in the second opening.

19. A method for manufacturing a semiconductor device, comprising:

forming a dummy fin structure over a substrate;

forming a cover layers on an upper surface of the substrate such that portions of the upper surface of the substrate around the fin structure is not covered by the cover layer;

forming first semiconductor layers on side surfaces of the dummy fin structure and the portions of the substrate not covered by the cover layer;

forming a first insulating layer over the substrate so that the dummy fin structure and the first semiconductor layers are embedded in the first insulating layer;

removing upper portions of the first insulating layer, the dummy fin structure and the first semiconductor layer;

after removing the upper portions of the first insulating layer, the dummy fin structure and the first semiconductor layer, removing the dummy fin structure to form a space and forming an additional insulating layer in the space, thereby forming two buffer structures made of the first semiconductor layers, the buffer structures having a fin-shape and extending along a first direction and arranged in parallel with each other in a second direction crossing the first direction, the buffer structures having a different lattice constant than the substrate; and

after forming the fin-shaped buffer structures, forming fin structures over upper surfaces of the fin-shaped buffer structures, respectively.

20. The method of claim 19 , wherein a width of each of the buffer structures along the second direction is greater than a width of each of the fin structures along the second direction measured at an interface between the buffer structures and the fin structures, the upper surfaces of the buffer structures being in contact with bottoms of the fin structures at the interface, respectively.