| 摘要 |
A lower portion of an interlayer insulating film is formed contiguous with a semiconductor wafer. The lower portion has a high impurity concentration and a high etching rate. An upper portion of an interlayer insulating film is formed over the lower portion apart from the semiconductor wafer. The upper portion has a low impurity concentration and a low etching rate. A plurality of contact holes are formed through the interlayer insulating film by anisotropic etching. The bottom portion of each contact hole is expanded by isotropic etching, and a contact is formed in the contact hole. Thus, a satisfactory contact is formed in a hole of a large aspect ratio.
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