A method of manufacturing a semiconductor device, includes: forming a first and second interconnect trenches adjacent to each other in an interlayer insulating film; providing a first interconnect and a space thereon within the first interconnect trench, and a second interconnect and a space thereon within the second interconnect trench; forming a first trench larger in width from the first interconnect trench and a second trench larger in width from the second interconnect trench, by conducting isotropic-etching; and forming a first insulating film within the first trench and a second insulating film within the second trench by filling an insulating material in the first trench and the second trench.