A semiconductor device manufacture method has the steps of: (a) coating a low dielectric constant low-level insulating film above a semiconductor substrate formed with a plurality of semiconductor elements; (b) processing the low-level insulating film to increase a mechanical strength of the low-level insulating film; (c) coating a low dielectric constant high-level insulating film above the low-level insulating film; and (d) forming a buried wiring including a wiring pattern in the high-level insulating film and a via conductor in the low-level insulating film. The low-level insulating film and high-level insulating film are made from the same material. The process of increasing the mechanical strength includes an ultraviolet ray irradiation process or a hydrogen plasma applying process.