A method for manufacturing a semiconductor device is provided to control amount and depth of impurity implantation according to a low voltage region and a high voltage region and to simplify an impurity implantation process according to a thickness of a photoresist pattern. A first photoresist pattern(110) for opening a low voltage region and a high voltage region is formed on a semiconductor substrate(100) on which an isolation layer(102) is formed. A second photoresist pattern(120) for opening only the high voltage region is formed on an upper side of the first photoresist pattern. An impurity implantation process is performed on the low voltage region and the high voltage region at the same time to form impurity implanted wells(112,122) on the low and high voltage regions. The first and second photoresist patterns are removed. Impurities are implanted into the respective wells on the low and high voltage regions with different concentration and depth according to thicknesses of the first and second photoresist patterns.