A method of double patterning a thin film is described. The method comprises forming a thin film to be patterned on a substrate, forming an anti-reflective coating (ARC) layer on the thin film, and forming a mask layer on the ARC layer. Thereafter, the mask layer is patterned to form a first pattern and a second pattern therein, and the first and second patterns are partially transferred to the ARC layer using a transfer process, such as an etching process or a developing process. Once the mask layer is removed, the first pattern and second patterns are completely transferred to the ARC layer using an etching process, and the first and second patterns in the ARC layer are transferred to the underlying thin film using another etching process.