Patent ID: 8518820

Claim:
A method of manufacturing a semiconductor device, the method comprising: forming an insulating layer over a substrate; coating a first photo resist layer over the insulating layer; using a first mask, patterning the first photo resist layer thereby forming first features oriented in a first direction, the first mask comprising a first plurality of lines oriented in the first direction; after patterning the first photo resist layer, coating a second photo resist layer; using a second mask, patterning the second photo resist layer thereby forming second features oriented in a second direction, wherein the second mask comprises a second plurality of lines oriented in the second direction orthogonal to the first direction, wherein the second mask is aligned relative to the first mask such that the first features are perpendicular to the second features; after patterning the second photo resist layer, coating a third photo resist layer; using a third mask, patterning the third photo resist layer thereby forming third features, wherein the first, the second, and the third features comprise a pattern for forming contact holes; and forming contact holes by etching the insulating layer using the first, the second, and the third features.