Low dosage field rings for high voltage semiconductor device

A termination structure for a semiconductor die;

• said semiconductor die having a body of silicon of one of the conductivity types and an upper N− epitaxial layer for receiving diffusions therein;
• said N− epitaxial layer having an active area diffused therein;
• a first electrode means connected to said active area;
• said active area having an outer periphery;
• said N− epitaxial area and said die having an outer peripheral street;
• said first electrode and said street being connectable to potential differences in excess of about 600 volts;
• said termination structure comprising a plurality of spaced concentric P type diffusion rings in said N− epitaxial layer surrounding said outer periphery of said active area to distribute the electric field between said first electrode and said street;
• said P type diffusion rings having a concentration produced by an implant dose of from about 2E12 to 2E13 atoms/cm2 to reduce the electric field at the surface of said N epitaxial layer and to prevent their complete depletion at full reverse voltage.