A semiconductor device including an insulated gate field effect transistor (IGFET) has been disclosed. The IGFET may be formed in an element region defined by an element isolation region (14) formed on a semiconductor substrate (8). A covering portion (10) may cover at least a portion of an end (22) of the element region. Covering portion (10) may be formed essentially of the same material as a side wall (10) of a gate (12) of the IGFET. A source/drain region (18) may be formed using gate (12) and covering portion (10) as a mask. In this way, a distance between an intra-substrate high-concentration contour line (20) and source/drain region (18) in area of end (22) of the element region may remain sufficient and an IGFET breakdown voltage may be improved.