A method for manufacturing a semiconductor device having an air gap, includes: providing a substrate having a first dielectric layer and a second dielectric layer formed thereon successively; forming a mask layer on the second dielectric layer; patterning the first and the second dielectric layer by using the mask layer as a mask so as to form a plurality of grooves; filling a conducting material into the grooves; removing redundant conducting material on the second dielectric layer utill the second dielectric layer is exposed so as to form a plurality of conductive trenches; forming a molecular sieve on the second dielectric layer and the conductive trenches; and removing the second dielectric layer partly or completely by flowing a reactant gas towards the second dielectric layer through the molecular sieve, so as to form an air gap. It is novel and simple to form an air gap through molecular sieve.