Semiconductor power device

A semiconductor power device comprising:

• a first base layer containing an impurity of a first conductivity type so as to have a concentration gradient which continuously changes in a thickness direction thereof;
• a second base layer containing an impurity of a second conductivity type formed in one surface region of said first base layer;
• an emitter layer containing an impurity of said first conductivity type formed in a surface region of said second base layer;
• a gate electrode continuously formed at least on said second base layer and said emitter layer;
• a collector layer formed on the other surface of said first base layer, said collector layer contains an impurity of said second conductivity type and has a thickness of 1 μm or less;
• a first main electrode formed on said second base layer;
• and
• a second main electrode formed on said collector layer.

A method for manufacturing a semiconductor power device comprising:

• introducing an impurity of a first conductivity type into a semiconductor substrate from one surface to form a first base layer, said first base layer having a concentration gradient which continuously changes in a thickness direction thereof;
• introducing an impurity of a second conductivity type into said first base layer to form a second base layer;
• introducing an impurity of said first conductivity type into said second base layer to form an emitter layer;
• forming a trench in said emitter layer, said trench having a depth that reaches through said second base layer to said first base layer;
• forming a gate electrode in said trench;
• forming a conductive layer on the resultant structure, then patterning said conductive layer to form a first main electrode continuously on said second base layer and said emitter layer;
• removing said first base layer from the other surface to provide a desired thickness of said first base layer;
• introducing an impurity of said second conductivity type into said other surface of said first base layer to form a collector layer;
• and
• forming a second main electrode on an exposed surface of said collector layer.