The etching selectivity is controlled by appropriately changing the dimension of the opening of each contact holes in forming simultaneously a plurality of contact holes of different depth by etching. By forming a dent in advance underlying the region where a contact hole is to be formed, the depth of the contact hole can be increased, whereby difference in the depths of the plurality of contact holes can be reduced. As a result, damage in the underlying layer or under etching in forming a plurality of contact holes of different depth simultaneously by etching can be solved.