The present invention provides a semiconductor device manufacturing method. This method comprises: etching a first dielectric layer to form a recess; depositing a second dielectric layer over said first dielectric layer and said recess, such that said recess is enclosed by said first dielectric layer and said second dielectric layer to form an air gap; and performing etching, such that a first trench is formed in said first dielectric layer and said second dielectric layer, adjacent to said air gap. The first trench can be filled with a conductive material to form wiring.