Method of forming three-dimensional lithographic pattern

A method of forming a dual damascene pattern, comprising:

• providing a substrate;
• forming a first photoresist layer on said substrate, said first photoresist layer corresponding to a first exposure removal dose;
• forming a second photoresist layer on said first photoresist layer, said second photoresist layer corresponding to a second exposure removal dose smaller than said first exposure removal dose;
• providing a reticle with multiple regions of different light transmittances;
• through said reticle, exposing said first photoresist layer and said second photoresist layer so as to form a first removable region in said first photoresist layer and a removable region in said second photoresist layer through one of said multiple regions of different light transmittances and to form a second removable region substantially only in said second photoresist layer through another one of said multiple regions of different light transmittances, respectively;
• developing said first photoresist layer and said second photoresist layer so as to remove said first removable region, said second removable region, and said removable region to form a patterned photoresist;
• and
• etching said substrate to form said patterned dual damascene pattern in said substrate by using said patterned photoresist as a mask.