The reliability of a porous Low-k film is improved. The mean diameter of first pores and second pores in an interlayer insulation film of a second fine layer including a porous Low-k film is set at 1.0 nm or more and less than 1.45 nm. This prevents the formation of a modified layer over the surface of the interlayer insulation film by process damages. Further, the formation of the moisture-containing modified layer is inhibited to prevent oxidation of a barrier film and a main conductor film forming respective wirings. This prevents deterioration of breakdown voltage between respective wirings. This prevents deterioration of the EM lifetime of wirings formed adjacent to the interlayer insulation film and the inter-wiring TDDB lifetime of the wirings.