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 . <EOS>