Semiconductor device having a planarized surface

Claim 1

A semiconductor device having a planarized surface, comprising: a semiconductor substrate; an interconnection layer portion provided on a surface of said semiconductor substrate and having a plurality of elements of at least one interconnection layer spreading horizontally, comprising a high density portion having a relatively high number of interconnection elements and a low density portion comprising a relatively low number of said interconnection elements; a first interlayer insulating film provided on said semiconductor substrate to cover both said high interconnection density portion and said low interconnection density portion and having an insulating film surface; a second interlayer insulating film provided over said first interlayer insulating film; wherein at said high interconnection density portion, each of said first and second interlayer insulating films comprises a first silicon oxide film, a silicon nitride film and a second silicon oxide film, formed in this order relative to said substrate surface; at said low interconnection density portion, said first interlayer insulating film includes said first silicon oxide film, said silicon nitride film, a PSG film and said second silicon oxide film, formed in this order relative to said substrate surface; variations in height, as determined from said surface of said semiconductor substrate to said first insulating film surface extending over said high and said low interconnection density portions are limited to be within a range of ±0.3 μm.