Semiconductor structure and method for forming the same, and memory and method for forming the same

1. A method for forming a semiconductor structure, comprising:

providing a substrate on which a sacrificial layer and an active layer located on the sacrificial layer are formed;

patterning the active layer to form several discrete active pillars;

removing the sacrificial layer to form a gap;

forming a bit line within the gap; and

forming a semiconductor pillar on the top of the active pillar;

wherein removing the sacrificial layer and forming the bit line further comprises:

etching the active layer and the sacrificial layer to form active lines extending in a first direction;

forming a first isolation layer filling the space between the active lines;

pattering the first isolation layers to form several holes within the first isolation layer between adjacent active lines, the sidewalls of the holes exposing the sacrificial layer;

removing the sacrificial layer along the hole to form a gap at the position of the sacrificial layer; and

filling a conductive material within the gap and the hole to form the bit line extending in the first direction and removing the conductive material within the hole.

2. The method for forming the semiconductor structure according to claim 1 , wherein the active layer is patterned for multiple times to form the active pillars, wherein at least one patterning step is performed after the bit line is formed.

3. The method for forming the semiconductor structure according to claim 1 , further comprising:

forming a first doped region located within the active pillar;

forming a channel region located within the semiconductor pillar and a second doped region located within a top region of the semiconductor pillar; and

forming a gate structure surrounding the channel region.

4. The method for forming the semiconductor structure according to claim 3 , wherein forming the first doped region comprises:

implanting ions into the active pillar to form the first doped region located within the active pillar; and

forming the second doped region comprises: implanting ions into the top region of the semiconductor pillar to form the second doped region located within the top region of the semiconductor pillar.

5. The method for forming the semiconductor structure according to claim 3 , wherein forming the first doped region comprises:

doping the active layer using an in-situ doping process to form a first doped layer during the process of forming the active layer using an epitaxial growth process; and

patterning the first doped layer into a first doped region after the active layer is patterned to form the active pillars.

6. The method for forming the semiconductor structure according to claim 3 , wherein forming the channel region and the second doped region comprises:

performing in-situ doping using an in-situ doping process to sequentially form the channel region and the second doped region during the process of forming the semiconductor pillar using an epitaxial growth process.

7. The method for forming the semiconductor structure according to claim 3 , wherein forming the gate structure comprises:

sequentially forming a gate dielectric layer and a gate layer on the surface of the semiconductor pillar; and

patterning the gate dielectric layer and the gate layer to form a gate structure surrounding the channel region within the semiconductor pillar, and expose the top region of the semiconductor pillar.

8. The method for forming the semiconductor structure according to claim 7 , wherein the gate structures on the surfaces of the semiconductor pillars located on the same column arranged in the second direction are connected.

9. The method for forming the semiconductor structure according to claim 3 , further comprising:

forming a second isolation layer covering the gate structure and the second doped region, the second isolation layer exposing the top surface of the second doped region.

10. The method for forming the semiconductor structure according to claim 1 , wherein forming the active pillar, removing the sacrificial layer, and forming the bit line further comprise:

etching the active layer and the sacrificial layer to form active lines extending in a first direction;

forming a first isolation layer filling the space between the active lines;

patterning the active lines to form several active pillars and several holes, the sidewalls of the holes exposing the sacrificial layer; removing the sacrificial layer along the hole to form a gap at the position of the sacrificial layer; and

filling a conductive material within the gap to form the bit line extending in the first direction.

11. The method for forming the semiconductor structure according to claim 1 , further comprising:

forming a through-hole at an end of the active line; and

filling a conductive material within the through-hole to form a bit line connection line, the bottom of the bit line connection line being connected with the bit line.

12. The method for forming the semiconductor structure according to claim 1 , wherein forming the active pillar further comprises:

after the bit line is formed, patterning the active lines to form several active pillars arranged in an array in a first direction and in a second direction.

13. The method for forming the semiconductor structure according to claim 1 , further comprising:

forming an isolation dielectric layer filling the space between the active pillars.

14. The method for forming the semiconductor structure according to claim 13 , wherein forming the semiconductor pillar comprises:

forming a protective layer on the surfaces of the isolation dielectric layer and the active pillar;

forming an epitaxial through-hole within the protective layer, the bottom of the epitaxial through-hole exposing a top surface of the active pillar;

epitaxially growing a semiconductor material on the top surface of the active pillar to form a semiconductor pillar located within the epitaxial through-hole; and

removing the protective layer.

15. The method for forming the semiconductor structure according to claim 13 , wherein forming the semiconductor pillar comprises:

forming a semiconductor material on the top surface of the active pillar; and

etching and trimming the semiconductor material to form a semiconductor pillar located on the top of the active pillar.