Semiconductor element with zone guard rings

A semiconductor element of disc shape having upper and lower surfaces and a peripheral surface, comprising:

• at least one pn junction with a higher doped conductivity zone on one side and a lower doped zone of the opposite conductivity on the other side, said pn junction extending to the peripheral surface;
• said lower doped zone having a surface forming a part of said lower surface and a part of said peripheral surface;
• at least one zone guard ring being established in said lower doped zone by a ring shaped region formed inside said lower doped zone, said ring-shaped region having a conductivity type opposite to that of said lower doped zone, and being bounded by parts of said lower and said peripheral surfaces, said surface parts of said lower and said peripheral surfaces bounding said at least one zone guard ring being without electrical contacts;
• and
• the pn junction and the at least one zone guard ring separated by an interval, a, selected small enough such that upon application of a reverse voltage to the pn junction the region of the semiconductor between the pn junction and the guard ring can be depleted of charge carriers at a voltage insufficient to cause junction breakdown.