| 摘要 |
A first trench is formed in an element-separating region on the surface of a semiconductor substrate, and a second trench is formed in an alignment mark region thereof. When a first insulating substance is deposited on the substrate surface so as to bury the first and second trenches, a first insulating film is formed into a recessed shape in both the first and second trenches. A second insulating substance having an etching rate slower than that of the first insulating substance is formed on the first insulating film, and further etched to leave the second insulating film only over the second trench. The overall thickness of the device is reduced in such a way that the upper surface of the first insulating film in the first trench becomes flush with the semiconductor substrate surface. A part of the surface of the insulating substance on the alignment mark portion projects so as to be usable as an alignment mark. Alternatively, when a first trench is formed extending to both the element-separating and alignment mark regions and further when an insulating film is deposited on the substrate surface so as to bury both the first and second trenches, a first projecting insulating film can be formed between the two trenches. A second insulating film whose etching rate is slower than that of the first insulating film is formed on the projecting insulating film and further etched to leave the second insulating film so as to cover only the first projecting insulating film. The overall thickness is reduced in such a way that the upper surface of the first insulating film becomes flush with the semiconductor substrate surface, and further the remaining second insulating film is removed. The remaining first insulating film is usable as an alignment mark portion.
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