PURPOSE: To form a contact hole in a semiconductor device so as to have a size nearly the same as the design dimensions.

CONSTITUTION: A polycrystalline silicon pad 6, an insulating film 7 and a polycrystalline silicon layer 8 are, formed on the main surface of a semiconductor substrate 1. An interlayer insulating film 3 is formed so as to cover the polycrystalline silicon layer 8. A mask layer is formed on the interlayer insulating film 3. The mask layer is used as a mask, and a part of the surface of the polycrystalline silicon layer 8 is exposed by etching the interlayer insulating film 3. A part of the insulating film 7 is exposed by etching and eliminating at the sane time the exposed polycrystalline silicon layer 8 and the mask layer. A part of the surface of the polycrystalline silicon pad 6 is exposed by etching a part of the surface of the exposed insulating film 7. Thereby contact holes 22 are formed, and then an aluminum wiring layer 9 is formed.