According to one embodiment of the present invention, a method of forming a semiconductor device is provided, the method including: forming a substrate; forming a first gate on the substrate; forming a mask layer on the substrate, the mask layer including a first window covering an area within which the first gate is formed so that the first gate divides the substrate exposed by the first window into a first region and a second region; and doping the exposed substrate using rays inclined with respect to the substrate top surface, where the position of the first gate with respect to a border of the first window is chosen such that the inclined doping rays impinge more on the first region than on the second region.