Mechanisms for forming patterns using multiple lithography processes

A method comprising:

• forming a target layer over a semiconductor substrate;
• forming a patterned first hard mask layer over the target layer;
• forming a first buffer layer over the patterned first hard mask layer;
• removing a first portion of the buffer layer to expose a portion of the target layer while a second portion of the buffer layer covers the patterned first hard mask layer;
• forming a patterned second hard mask layer directly on the exposed portion of the target layer;
• removing the second portion of the first buffer layer from over the patterned first hard mask layer;
• etching through the patterned first hard mask layer to form a first trench in the target layer such that the patterned second hard mask layer protects a first portion of the target layer underlying the patterned second hard mask layer;
• and
• prior to etching through the patterned first hard mask layer to form the first trench in the target layer, etching through the patterned second hard mask layer to form a second trench in the target layer such that the patterned first hard mask layer protects a second portion of the target layer underlying the patterned first hard mask layer.

A method comprising:

• forming a target layer over a semiconductor substrate, wherein the target layer is formed of a material selected from the group consisting of a dielectric material and a metallic material;
• forming a patterned first hard mask layer directly on the target layer;
• forming a first buffer layer directly on the patterned first hard mask layer and directly on a portion of the target layer;
• removing a first portion of the buffer layer to expose the portion of the target layer while a second portion of the buffer layer covers the patterned first hard mask layer;
• forming a patterned second hard mask layer directly on the exposed portion of the target layer and directly on a top surface of the second portion of the buffer layer;
• removing the patterned second hard mask layer from the top surface of the second portion of the buffer layer;
• removing the second portion of the first buffer layer from over the patterned first hard mask layer;
• etching through the patterned first hard mask layer to form a first trench in the target layer such that the patterned second hard mask layer protects a first portion of the target layer underlying the patterned second hard mask layer;
• and
• prior to etching through the patterned first hard mask layer to form the first trench in the target layer, etching through the patterned second hard mask layer to form a second trench in the target layer such that the patterned first hard mask layer protects a second portion of the target layer underlying the patterned first hard mask layer.