Method of fabricating patterned structure

A method of fabricating a patterned structure, comprising:

• forming a first pattern transfer layer on a material layer;
• forming a second pattern transfer layer on the first pattern transfer layer;
• performing a first patterning process to the second pattern transfer layer, wherein a part of the second pattern transfer layer is patterned to be a first pattern by the first patterning process;
• forming a first spacer on sidewalls of the first pattern;
• performing a second patterning process to the first pattern transfer layer after forming the first spacer, wherein the first pattern transfer layer is patterned to be a second pattern and a third pattern by the second patterning process, and the second pattern is formed between the material layer and the first pattern;
• forming a cover layer covering the first pattern, the first spacer, the second pattern, and the third pattern;
• removing a part of the cover layer for exposing the first pattern and the first spacer;
• removing the first spacer;
• and
• performing a third patterning process to the first pattern transfer layer with the first pattern and the cover layer as a mask after removing the first spacer, wherein the second pattern is patterned to be a fourth pattern by the third patterning process.