| 摘要 |
PURPOSE:To set to the necessary minimum limit withstand voltage and to prevent a damage from occurring due to the concentration of a breakdown current by providing a region made of a high density impurity by the first conductive type substrate to contact directly with the second conductive type high density impurity region. CONSTITUTION:A P<+> type field inversion preventive layer 22, a field oxide film 23, a gate oxide film 24 and a gate oxide 25 are formed on the surface of a P type silicon substrate 21. Boron ions are implanted to form P<+> type impurity regions 29, 30 arsenic ions are implanted to form N<+> type impurity regions 31, 32 phosphorus ions are implanted to form N<-> type impurity regions 33, 34 to form a source region 35 and a drain region 36. The regions 29, 30 are disposed to contact directly under the regions 31, 33. An interlayer insulating film 37 is formed, and an N-channel field effect transistor is formed by forming an aluminum electrode 39. Thus, the withstand voltage of the N<+>-P<-> junction is determined by the density of the P<+> region 30, and the withstand voltage can be controlled to the prescribed value by the forming conditions of the region 30. |
