A semiconductor device includes an interlayer insulating film formed on or over a semiconductor substrate. An opening is formed in the interlayer insulating film and reaches a lower layer metal wiring conductor. A metal plug is formed by filling the opening with Cu containing metal via a barrier metal. The interlayer insulating film includes the insulating film which includes a carbon containing silicon oxide (SiOCH) film which has Si--CH2 bond in the carbon containing silicon oxide film. The proportion of Si--CH2 bond (1360 cm-1) to Si--CH3 bond (1270 cm-1) in the insulating film is in a range from 0.03 to 0.05 measured as a peak height ratio of FTIR spectrum.