| 摘要 |
PURPOSE:To make the thickness of an n<-> type epitaxial layer (a drain region) effectively thick and to enhance a breakdown strength value by a method wherein a second p<+> type region whose impurity concentration is higher than that of a first p-type well region is formed inside the first p-type well region whose impurity concentration is low and an n<+> type source region is formed on an outer-layer part of the second well region. CONSTITUTION:A cell 1 is constituted by the following: a first p-type well region 4 formed to be a dual structure on an outer-layer part of an n<-> type epitaxial layer 3 formed on a main face of an n<+> type silicon substrate 2; a second p<+> type well region 5; an n<+> type source region 6 formed to be a frame shape on an outer-layer part at the periphery of the second well region 5. An impurity concentration value of the first well region 4 is about 10<17>cm<-3> and its depth is about 3mum; an impurity concentration value of the second well region 5 is high at about 10<17>cm<-3> and its depth is about 2mum. Because the second well region 5 is formed to be shallow, the thickness of the n<->-type epitaxial layer 3 is effectively thick; when a device is operated, its breakdown strength value is enhanced because a depletion layer in a base region can be expanded. |
