a flat - pack type gto thyristor has an external cathode electrode placed on a semiconductor element . the top surface of the external cathode electrode has a three - level step configuration . when a cathode member of an external electric equipment is pushed onto the external cathode electrode , no force is applied to the lower two steps in the step configuration . consequently , the peripheral portion of the external cathode electrode is not deformed and the semiconductor element does not become unstable in gate characteristics .