| 摘要 |
PURPOSE:To enable to stepwisely and reversibly control a breakdown voltage in values capable of being arbitrarily set by forming electrodes on a ring region of a diode having a guard ring structure to be able to connect between main electrodes. CONSTITUTION:A P type region 2 which has a large area and an annular P type region 3 which surrounds the region 2 are formed in an N type silicon substrate 1. In this case, when two breakdown voltage to be set for an element are VAV1, VAV2, the resistivity, the junction depth and lateral size are selected so that the breakdown voltage of a diode of guard ring type become VAV1 and the breakdown voltage of the junction between the region 3 and the substrate 1 become VAV2. When a switch 7 is opened, the breakdown voltage of the element becomes VAV1 when a reverse voltage is applied between an anode terminal A and a cathode terminal K. When the switch 7 is closed to shortcircuit between A and C, an anode electrode 4 and a guard ring electrode 5 of a diode become equal voltage. Accordingly, the breakdown voltage of the element becomes low to VAV2. This switching is reversible. |
