Provided is a semiconductor integrated circuit device, which includes: a low-voltage MOS transistor having a source/drain region formed of a low impurity concentration region and a high impurity concentration region; and a high-voltage MOS transistor similarly having a source/drain region formed of a low impurity concentration region and a high impurity concentration region, in which, the source/drain high impurity concentration region of the low-voltage NMOS transistor is doped with arsenic, while the source/drain high impurity concentration region of the high-voltage NMOS transistor is doped with phosphorus.