Semiconductor devices and methods of forming semiconductor devices are provided in which a plurality of patterns are simultaneously formed to have different widths and the pattern densities of some regions are increased using double patterning. The semiconductor device includes a plurality of conductive lines each including a first line portion and a second line portion, where the first line portion extends on a substrate in a first direction, the second line portion extends from one end of the first line portion in a second direction, and the first direction is different from the second direction; a plurality of contact pads each of which is connected with a respective conductive line of the plurality of conductive lines via the second line portion of the corresponding conductive line; and a plurality of dummy conductive lines each including a first dummy portion extending from a respective contact pad of the plurality of contact pads, in parallel with the corresponding second line portion in the second direction.