There is provided a method for manufacturing a semiconductor device having a high breakdown voltage transistor and a low breakdown voltage transistor provided on a same semiconductor substrate. The method includes forming a first gate electrode of the high breakdown voltage transistor and a second gate electrode of the low breakdown voltage transistor on a transistor formation area of the substrate, as well as a dummy gate electrode on a dummy pattern formation area of the substrate; forming an interlayer insulation film on the substrate so as to cover the first and the second gate electrodes and the dummy gate electrode; and forming a first contact hole on the first gate electrode, a second contact hole on the second gate electrode, and a dummy contact hole on the dummy gate electrode, respectively, by partially dry etching the interlayer insulation film, wherein in the formation of the contact holes, a top surface of the dummy gate electrode is exposed at a bottom of the dummy contact hole before a top surface of the first gate electrode is exposed at a bottom of the first contact hole.