| 摘要 |
PURPOSE:To prevent the breakdown of elements due to a breakdown current and improve the withstand voltage against a surge by a method wherein a diode region wherein a high concentration region of the first conductivity type and that of the second one are put into a P-N junction over a relatively wide plane is lamination-formed on the side of the main surface opposite to the first main surface side with the formation of the source region and the drain region of a semiconductor substrate. CONSTITUTION:When a high voltage such as surge is impressed between the drain and source, depletion layers 33 and 34 generate at the P-N<+> junction between the drain region 23 and the substrate 21 and the P<+>N<+> junction between a P<+> type layer 30 and an N<+> type layer 31, respectively. Then, an electric field concentrates at the gate side edge 35 of the drain region 23; however, since a Zener diode ZD1 is composed by the P-N junction of the semiconductor layers 30 and 31 both of high concentrations, the breakdown occurs at the P<+> N<+> junction surface 36. At this time, the breakdown current BI flows uniformly over the whole of the P<+>N<+> junction surface 36, therefore heat concentration does not occur, and the breakdown current BI does not flow in the neighborhood of an element forming surface on the side of the upper surface of the substrate 21. |
