Method for forming semiconductor structure by using sacrificial layer configured to be replaced subsequently to form bit line, semiconductor structure, and memory

A method for forming a semiconductor structure, comprising:

• providing a substrate, wherein a sacrificial layer and an active layer located on a surface of the sacrificial layer are formed on the substrate;
• etching the active layer and the sacrificial layer up to a surface of the substrate to form a plurality of active lines arranged in parallel and extending along a first direction;
• filling an opening located between two adjacent ones of the plurality of active lines to form a first isolating layer;
• etching an end of each of the plurality of active lines to form opening holes exposing the surface of the substrate, a side wall of the opening holes exposing the sacrificial layer;
• removing the sacrificial layer along the opening holes, to form a gap between a bottom of the plurality of active lines and the substrate;
• filling a conductive material in the gap to form a bit line extending along the first direction;
• patterning the plurality of active lines to form a plurality of separate active pillars that are arrayed along the first direction and a second direction;
• forming semiconductor pillars on top surfaces of respective ones of the plurality of separate active pillars;
• forming a first doped region in the plurality of separate active pillars;
• forming a channel region above the first doped region and a second doped region above the channel region in the semiconductor pillars;
• and
• forming a gate structure surrounding the channel region;
• and
• forming a second isolating layer covering the gate structure and the second doped region, the second isolating layer exposing a top surface of the second doped region.