Forming a semiconductor device of the present invention for forming a forming a first hard mask layer on a semiconductor substrate including a cell region and peripheral circuit region, the spacer pattern on the top of the first hard mask layer in the cell area steps and, a step of forming a cell open mask pattern to open the cell region on the peripheral circuit region, the first hard mask layer and the spacer pattern in the exposed by the cell open mask pattern wherein the cell region as a mask, etching the first and forming a hard mask pattern, and forming a second hard mask layer on the first hard mask layer above the first hard mask pattern and the peripheral circuit region of the cell region, the second and forming a cut mask pattern to the hard mask layer above, the cutting mask pattern to said second hard mask layer as an etch mask, the first of said cell region first hard mask pattern, the first hard mask layer in the peripheral circuit region, and including the step of forming the active region and the device isolation region in the peripheral circuit region in the cell areas by etching the semiconductor substrate, the active region and the device isolation region in the step of forming the active region of the cell region has a 6F2 structure to enhance the uniformity improving the characteristics of the semiconductor element and, by reducing the process time and costs and provides an effect of increasing the mass-productivity of semiconductor devices.