In a method of forming micro patterns of a semiconductor device, first etch mask patterns are formed over a semiconductor substrate. An auxiliary film is formed over the semiconductor substrate including a surface of the first etch mask patterns. Second etch mask patterns are formed between the auxiliary films formed on sidewalls of the first etch mask patterns. The first etch mask patterns and the second etch mask patterns are formed using the same material. The auxiliary films between the first and second etch mask patterns are removed. Accordingly, more micro patterns can be formed than allowed by the resolution limit of an exposure apparatus while preventing misalignment.