Semiconductor device with enhanced breakdown voltage

A semiconductor device comprising:

• a semiconductor element formed on a semiconductor substrate;
• and
• a peripheral structure provided around said semiconductor element,
• said peripheral structure comprising:
• a first electrode formed on a peripheral portion of said peripheral structure and electrically connected to said semiconductor substrate;
• an insulating film formed on said semiconductor substrate between a forming region of said semiconductor element and said first electrode;
• a multistage back-to-back diode formed locally in a partial region on said insulating film and extending in a first direction so as to be connected between said first electrode and a second electrode that is the outermost electrode on said semiconductor substrate in said semiconductor element;
• guard rings formed in said semiconductor substrate to surround said semiconductor element;
• and
• at least two impurity regions formed locally in a region including the vicinity of said back-to-back diode in said semiconductor substrate, said at least two impurity regions being formed in the first direction between an adjacent pair of said guard rings in the vicinity of said back-to-back diode such that said adjacent pair of guard rings are separated from each other in the first direction by said at least two impurity regions, said at least two impurity regions each being of a substantially linear shape extending in a second direction transverse to the first direction and of the same conductivity type as said guard rings, said substantially linear shape of each one of said at least two impurity regions not intersecting with said adjacent pair of guard rings, and said substantially linear shape of each one of said at least two impurity regions having a finite length with discrete endpoints at which said at least two impurity regions respectively terminate in said region.