Semiconductor device and fabrication process thereof

A method of fabricating a semiconductor device comprising a semiconductor substrate of a first conductivity type, a well of said first conductivity type formed in said semiconductor substrate, a transistor formed in said well, a diffusion region of a second conductivity type formed in said semiconductor substrate so as to cover a lateral side surface and a bottom edge of said well, a terminal formed on said semiconductor substrate at an outside part of said diffusion region, and a conductive region contacting with said well, said well being in ohmic contact with said terminal via said conductive region and said semiconductor substrate, said conductive region having an impurity concentration level exceeding an impurity concentration level of said semiconductor substrate, said method comprising the steps of:

• forming a conductive region in said semiconductor substrate by introducing a first impurity element of a first conductivity type;
• and
• forming said diffusion region by introducing a second impurity element of second conductivity type into said semiconductor substrate.