PURPOSE: To prevent the deterioration of wiring form and the generation of a stringer in a subsequent process by decreasing the level difference of an interlayer insulating film due to etching.

CONSTITUTION: A silicon nitride film is formed on an interlayer insulating film 9, and the silicon nitride film 10 can be sloped by isotropically etching the silicon nitride film 10, and upon anisotropic etching of the remaining silicon nitride film and the interlayer insulating film 9, the etching start time for the interlayer insulating film 9 under the film 10 varies with the thickness of the silicon nitride film 10, and the etching state of the film 9 can also be sloped in response to the slope of the silicon nitride film 10. At the same time, absolute level difference can be decreased, a wiring layer formation state in a subsequent process can be improved, and the risk of disconnection is eliminated and the generation of a stringer can also be prevented.