Semiconductor device and method of manufacturing semiconductor device

A method of manufacturing a semiconductor device having an insulated gate bipolar transistor portion and a freewheeling diode portion formed on a semiconductor substrate, the insulated gate bipolar transistor portion including

• a drift layer of a first conductivity type formed in the semiconductor substrate;
• a base layer of a second conductivity type formed on a front surface side of the semiconductor substrate;
• an emitter region of the first conductivity type selectively formed in the base layer;
• at least one gate electrode formed on the front surface side of the semiconductor substrate each with a gate insulating film formed therebetween;
• an emitter electrode electrically connected to both the base layer and the emitter region;
• a collector region of the second conductivity type selectively formed on a rear surface side of the semiconductor substrate;
• and
• a collector electrode electrically connected to the collector region;
• and
• the freewheeling diode portion including
• an anode layer of the second conductivity type formed on the front surface side of the semiconductor substrate and electrically connected to the emitter electrode;
• and
• a cathode region of the first conductivity type selectively formed on the rear surface side of the semiconductor substrate and electrically connected to the collector electrode,
• the method comprising:
• providing the semiconductor substrate;
• introducing an impurity of the first conductivity type to a rear surface of the semiconductor substrate;
• performing first heat treating to activate the impurity, and forming a field stop layer of the first conductivity type at a position deeper than that of the collector region from the rear surface of the semiconductor substrate, the field stop layer having an impurity concentration higher than that of the drift layer;
• performing a first irradiation to irradiate light ions from the rear surface of semiconductor substrate, and forming, in the semiconductor substrate, a first low-lifetime region;
• performing a second irradiation to irradiate the light ions from the rear surface of the semiconductor substrate, and forming, in the field stop layer, a second low-lifetime region, each of the first and second low-lifetime regions having a carrier lifetime thereof shorter than that of any region of the semiconductor device other than the first and second low-lifetime regions;
• and
• performing second heat treating to reduce a density of defects generated in the field stop layer when the second irradiation is performed.