Patent ID: 7867890

Claim:
A method for manufacturing a semiconductor memory device, comprising the following steps of: forming a memory cell area including at least one memory cell, and a peripheral area including at least one peripheral transistor, in a semiconductor substrate; forming a first insulating film over the semiconductor substrate; forming a plurality of wirings over the first insulating film so as to adjoin one another, a distance between the wirings in the memory cell area being smaller than a distance between the wirings in the peripheral area; forming a second insulating film over the first insulating film by a plasma CVD method and covering the wirings with the second insulating film to form air gaps between the respective adjacent wirings disposed only over the memory cell area; forming a third insulating film over the second insulating film by a high density plasma CVD method; and forming a fourth insulating film higher in moisture resistance than the second and third insulating films over the third insulating film.