Patent ID: 7592683

Claim:
A semiconductor device comprising: a first semiconductor region ( 15 ) of a first conductive type; a second semiconductor region ( 21 ) of a second conductive type formed on said first semiconductor region ( 15 ); a third semiconductor region ( 13 ) of the first conductive type formed in a surface region of said second semiconductor region ( 21 ) along an outer periphery of said second semiconductor region ( 21 ), and having a higher impurity concentration than that of said first semiconductor region ( 15 ); a fourth semiconductor region ( 14 ) of the first conductive type formed adjacent to a bottom surface of said third semiconductor region ( 13 ), and having a higher impurity concentration than that of said first semiconductor region ( 15 ); a fifth semiconductor region ( 19 ) of the first conductive type formed in the surface region of said second semiconductor region ( 21 ); a sixth semiconductor region ( 23 ) of the second conductive type formed in a surface region of said fifth semiconductor region ( 19 ); a first electrode ( 2 ) electrically connected to said second semiconductor region ( 21 ); a second electrode ( 4 ) electrically connected to said sixth semiconductor region ( 23 ); and a control electrode ( 3 ) laid out on said fifth semiconductor region ( 19 ) through an insulating film ( 31 ), an eighth semiconductor region ( 12 ) of the first conductive type formed in the surface region of said fifth semiconductor region ( 19 ) and having a higher impurity concentration than that of the fifth semiconductor region ( 19 ), wherein said fourth semiconductor region ( 14 ) is formed in said first semiconductor region ( 15 ) and said second semiconductor region ( 21 ), and has a protrusive piece ( 14 a ) so formed as to extend closer to said first electrode ( 2 ) side than said third semiconductor region ( 13 ), and a portion ( 14 b ) so formed as not to extend closer to said first electrode ( 2 ) than said protrusive piece ( 14 a ), said fifth semiconductor region ( 19 ) has regions ( 19 b ) including said sixth semiconductor region ( 23 ) and said eighth semiconductor region ( 12 ), and regions ( 19 a ) not including said sixth semiconductor region ( 23 ) and said eighth semiconductor region ( 12 ), and both regions are formed as to be alternately and apart from each other, and said eighth semiconductor region ( 12 ) is electrically connected to a back gate electrode ( 5 ).