Semiconductor device and method for manufacturing the same

A method for manufacturing a semiconductor device, comprising:

• forming a trench on an upper surface of a semiconductor layer having a first conductivity type semiconductor region;
• forming an insulating region filling the trench;
• forming a groove in the insulating region;
• depositing a conductive material in the groove to form a conductive portion;
• removing a part of the insulating region to expose an upper portion of the conductive portion;
• forming a first insulating film on one inner wall of the trench, a second insulating film on the other inner wall of the trench, and a third insulating film on the exposed conductive portion;
• depositing a conductive material in a groove between the first insulating film and the third insulating film to form a first gate conductive portion;
• depositing a conductive material in a groove between the second insulating film and the third insulating film to form a second gate conductive portion;
• implanting ions of a second conductivity type impurity to the semiconductor region to form a base region;
• implanting ions of a first conductivity type impurity to the base region to form a source region in an upper portion of the base region;
• and
• removing the conductive portion until an upper surface of the conductive portion is located below the first and second gate conductive portions to form a cavity extending from an upper end in a thickness direction of the semiconductor layer and having a tapered portion whose width increases as it goes from an upper surface toward a lower surface of the semiconductor layer.

A method for manufacturing a semiconductor device, comprising:

• forming a trench on an upper surface of a semiconductor layer having a first conductivity type semiconductor region;
• forming an insulating region filling the trench;
• forming a groove in the insulating region;
• depositing a conductive material in the groove and removing the conductive material up to a region below a region where a gate electrode is to be formed to form a conductive portion;
• forming an etching stopper film on the conductive portion;
• forming a second conductive portion on the etching stopper film;
• removing a part of the insulating region to expose the second conductive portion;
• forming a first insulating film on one inner wall of the trench, a second insulating film on the other inner wall of the trench, and a third insulating film on the exposed second conductive portion;
• depositing a conductive material in a groove between the first insulating film and the third insulating film to form a first gate conductive portion;
• depositing a conductive material in a groove between the second insulating film and the third insulating film to form a second gate conductive portion;
• implanting ions of a second conductivity type impurity to the semiconductor region to form a base region;
• implanting ions of a first conductivity type impurity to the base region to form a source region in an upper portion of the base region;
• and
• removing the second conductive portion formed on the etching stopper film to form a cavity extending from an upper end in a thickness direction of the semiconductor layer and having a tapered portion whose width increases as it goes from an upper surface toward a lower surface of the semiconductor layer.