In a method of forming patterns of a semiconductor device, an object layer is formed on a substrate. A plurality of guiding pillars and at least one guiding dam are formed on the object layer. A self-aligned layer including a block copolymer is formed in a space between the guiding pillars and the guiding dam, such that first blocks aligned around the guiding pillars and second blocks aligned around the guiding dam are formed. A trim pattern at least partially covering the guiding dam is formed. The first blocks are transferred in the object layer.