Patent ID: 7132327

Claim:
A method of making a semiconductor device, the method comprising: providing a water with a first layer, forming a non-patterned first hard mask over the first layer; forming a second hard mask stack over the non-patterned first hard mask; patterning the second hard mask stack according to a first pattern, wherein the patterning includes a first partial etching of the second hard mask stack to a first thickness; patterning for a second time, the second hard mask stack according to a second pattern, wherein the patterning for a second time includes a second partial etching of the second hard mask stack to a second thickness; blanket etching the second hard mask stack to form a first plurality of pattern structures of the second hard mask stack after the patterning for a second time, wherein the blanket etch also partially etches into portions of the first hard mask exposed by the blanket etch; etching the first hard mask with the first plurality of pattern structures to form a second plurality of pattern structures of the first hard mask, without substantially etching portions of the first layer exposed by the etching of the first hard mask; and etching the first layer with the second plurality of pattern structures to form a third plurality of pattern structures of the first layer, wherein portions of the wafer exposed by the etching of the first layer are kept substantially unharmed during the etching of the first layer, wherein the first hard mask includes a first material, the second hard mask stack includes a second material, and the first material is selectively etchable from the second material and the second material is selectively etchable from the first material, and wherein the first material is selectively etchable from the material of the first layer, allowing reduction of etch depth differences in the second plurality of pattern structures of the first hard mask prior to forming a third plurality of pattern structures in the first layer.