Lowe, Price, LeBlanc & Becker
Contact via for semiconductor device
 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. 
Mitsubishi Denki Kabushiki Kaisha
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Shinya
Watanabe