| 摘要 |
PURPOSE:To improve the withstand voltage of a thyristor without increasing the forward on voltage thereof by forming high density layers on nB-type layer and pB-type layer, respectively to eliminate abnormal expansion of a depletion layer in eliminated state. CONSTITUTION:High density n-type layers 14a, 14b having higher n-type impurity density than an nB-type layer 2 are formed at least at two positions in band-like shape at the periphery of the layer 2. A high density p-type layer 15 having higher p-type impurity than a pB-type layer 3 is formed in ring shape on the main surface of the layer 3. When a negative surface charge 9 is existed in the interior of the surface protective material 5, positive voltage is applied to the anode side metal 6, and negative voltage is applied to the cathode side metal 7. When there are existed the layers 14a, 14b thereon, the electron density in the vicinity of the surface of the layer 2 reduced due to the coulomb force by the charge 9 can be compensated not to reach the punch through phenomenon thereat. |
