Field effect transistor having high breakdown withstand capacity

Abstract

A field effect transistor having a high breakdown withstand capacity is provided. An active region is surrounded by a fixed potential diffusion layer , and a channel region is formed in the active region . A gate pad is provided outside the fixed potential diffusion layer . Minority carriers injected at a peripheral region of the active region flow into the fixed potential diffusion layer , which prevents breakdown attributable to concentration of the carriers. The fixed potential diffusion layer is surrounded by a plurality of guard ring diffusion layers through , and a pad diffusion layer formed in a position under the gate pad is connected to the innermost guard ring diffusion layer . Since this encourages expansion of a depletion layer under the gate pad , an increased breakdown voltage is provided.