Method of fabricating a bipolar transistor having a high ion concentration buried floating collector

A method of fabricating a semiconductor device, comprising the steps of:

• (a) selectively forming a plurality of first insulating films on a semiconductor substrate of a first conductivity type;
• (b-1) forming a principal buried layer of a second conductivity type having a relatively high concentration of defects formed in said semiconductor substrate;
• (b-2) forming secondary buried layers of relatively low concentration on upper and lower surfaces of said principal buried layer;
• and
• (c) forming a bipolar transistor including a first semiconductor layer of said second conductivity type having a relatively low concentration formed on said principal buried layer, a second semiconductor layer of said first conductivity type selectively formed on a surface of said first semiconductor layer, and a third semiconductor layer of said second conductivity type selectively formed on a surface of said second semiconductor layer.