Described in the present invention is a semiconductor device in which a plurality of interconnect lines are disposed, through an insulating layer, on the same layer above a semiconductor substrate having a semiconductor element; a first interlevel insulator is formed selectively in a narrowly-spaced region between adjacent interconnect lines; a second interlevel insulator is formed in a widely-spaced region between said adjacent interconnect lines, and the first interlevel insulator has a smaller dielectric constant than the second interlevel insulator. According to such a constitution, strength and reliability can be heightened and performance can be improved easily even in a miniaturized interconnect structure.