A manufacturing method of a semiconductor structure, comprising: providing a substrate, a plurality of spaced first trenches being formed in the substrate, and the first trenches extending along a first direction; forming a sacrificial layer in the first trenches and a first protective layer on the sacrificial layer, the sacrificial layer and the first protective layer filling up the first trenches, and the first protective layer in the first trenches being provided with etching holes penetrating through the first protective layer; removing the sacrificial layer via the etching holes to form air gaps; and carrying out a silicidation reaction on the substrate between adjacent ones of the first trenches and close to bottoms of the first trenches, so as to form, in the substrate, bit lines, BLs, extending along the first direction, parts of side surfaces of the BLs being exposed in the air gaps; characterized in that, the carrying out a silicidation reaction on the substrate between adjacent ones of the first trenches and close to bottoms of the first trenches, so as to form, in the substrate, BLs extending along the first direction, parts of side surfaces of the BLs being exposed in the air gaps, comprises: etching the substrate and the first protective layer to form a plurality of spaced second trenches, the second trenches extending along a second direction and not communicating with the air gaps; forming a second protective layer on sidewalls of the second trenches, the second protective layer in the second trenches enclosing third trenches; and depositing metal on bottoms of the third trenches, and carrying out the silicidation reaction by annealing to form the BLs. providing a substrate, a plurality of spaced first trenches being formed in the substrate, and the first trenches extending along a first direction; forming a sacrificial layer in the first trenches and a first protective layer on the sacrificial layer, the sacrificial layer and the first protective layer filling up the first trenches, and the first protective layer in the first trenches being provided with etching holes penetrating through the first protective layer; removing the sacrificial layer via the etching holes to form air gaps; and carrying out a silicidation reaction on the substrate between adjacent ones of the first trenches and close to bottoms of the first trenches, so as to form, in the substrate, bit lines, BLs, extending along the first direction, parts of side surfaces of the BLs being exposed in the air gaps; characterized in that, the carrying out a silicidation reaction on the substrate between adjacent ones of the first trenches and close to bottoms of the first trenches, so as to form, in the substrate, BLs extending along the first direction, parts of side surfaces of the BLs being exposed in the air gaps, comprises: etching the substrate and the first protective layer to form a plurality of spaced second trenches, the second trenches extending along a second direction and not communicating with the air gaps; forming a second protective layer on sidewalls of the second trenches, the second protective layer in the second trenches enclosing third trenches; and depositing metal on bottoms of the third trenches, and carrying out the silicidation reaction by annealing to form the BLs. etching the substrate and the first protective layer to form a plurality of spaced second trenches, the second trenches extending along a second direction and not communicating with the air gaps; forming a second protective layer on sidewalls of the second trenches, the second protective layer in the second trenches enclosing third trenches; and depositing metal on bottoms of the third trenches, and carrying out the silicidation reaction by annealing to form the BLs.