Patent ID: 8921213

Claim:
A method of making a semiconductor device, in which an electric current gain is less dependent upon an electric current, comprising: forming a first semiconductor region having a first surface, a first thickness and a first conductivity; forming a second semiconductor region having a second surface, a second thickness, an opposite conductivity opposite to the first conductivity and in contact with the first semiconductor region at a part of the first surface; forming a third semiconductor region having a third surface, a third thickness, the first conductivity and in contact with the second semiconductor region at a part of the second surface; making an impurity concentration of the third semiconductor region to be larger than a part of the second semiconductor region which is in contact with the third semiconductor region; forming a fourth semiconductor region having a fourth surface, a fourth thickness, an opposite conductivity type and in contact with the second semiconductor region at a part of the second surface; and making the fourth semiconductor region so as to be separated from the third semiconductor region and to enclose the third semiconductor region within a distance of minority carrier diffusion length of the second semiconductor region and making an impurity concentration of the fourth semiconductor region larger than that of the second semiconductor region.