Semiconductor device including a field effect transistor having a protective diode between source and drain thereof

A semiconductor device comprising;

• a semiconductor substrate of one conductivity type;
• a first semiconductor region of the other conductivity type formed in a main surface of said semiconductor substrate;
• a second semiconductor region of said one conductivity type formed in a surface of said first semiconductor region;
• a gate electrode formed on a portion of said first semiconductor region, said portion located between said second semiconductor region and said semiconductor substrate;
• a third semiconductor region of said one conductivity type formed in said main surface of said semiconductor substrate and said surface of said first semiconductor region, said third semiconductor region having higher impurity concentration than said semiconductor substrate and said third semiconductor region being in contact with both said semiconductor substrate and said first semiconductor region to form a Zener diode;
• a first electrode connected to said first and second semiconductor region;
• and
• a second electrode connected to said semiconductor substrate.