Patent ID: 6384431
Filing Date: 2002-05-07
Classification: H01L

Abstract:
An insulated gate bipolar transistor comprising:a first semiconductor layer having a first conductivity type; a second semiconductor layer formed on the first semiconductor layer, and having a second conductivity type; a third semiconductor layer formed on the second semiconductor layer, and having the second conductivity type; a fourth semiconductor layer formed on the third semiconductor layer, and having the second conductivity type; a fifth semiconductor layer formed in a surface side of the fourth semiconductor layer, and having the first conductivity type; a sixth semiconductor layer formed in a surface side of the fifth semiconductor layer, and having the second conductivity type; and an insulated gate structure for defining a channel region at the surface side of the fifth semiconductor layer between the fourth semiconductor layer and the sixth semiconductor layer, wherein a gradient of impurity concentration at a boundary region between the third semiconductor layer and the fourth semiconductor layer is set to 1Ã—1014 cmâˆ’3/&mgr;m(=1Ã—1018 cmâˆ’4) or less, and wherein an impurity concentration of the third semiconductor layer is lower than an impurity concentration of the second semiconductor layer, and the impurity concentration of the third semiconductor layer is higher than an impurity concentration of the fourth semiconductor layer.