Semiconductor device and manufacturing method thereof

A method of manufacturing a semiconductor device forming a MISFET, comprising:

• forming a cavity inside a semiconductor substrate;
• forming a hole in the semiconductor substrate, the hole being connected to the cavity;
• forming a back gate insulating film on surfaces of the semiconductor substrate which are exposed from the cavity and hole;
• forming a back gate electrode in the cavity and hole having surfaces covered with the back gate insulating film;
• forming a dummy gate in a region on the semiconductor substrate in which a gate electrode of the MISFET is to be formed;
• implanting impurities into portions of the semiconductor substrate which are not covered with the dummy gate, to form source and drain regions;
• forming an interlayer insulating film around the dummy gate;
• selectively removing the dummy gate, to form a gate groove having sidewalls made of the interlayer insulating film and exposing the semiconductor substrate and the back gate electrode;
• forming a front gate insulating film at a bottom surface of the gate groove;
• partially etching the front gate insulating film at the bottom surface of the gate groove, to form a contact hole connected to the back gate electrode;
• and
• forming a front gate electrode having a different work function from that of the back gate electrode in the gate groove and contact hole.

A method of manufacturing a semiconductor device forming a MISFET, comprising:

• forming a cavity inside a semiconductor substrate;
• forming a hole in the semiconductor substrate, the hole being connected to the cavity;
• forming a back gate insulating film on surfaces of the semiconductor substrate which are exposed from the cavity and hole;
• forming a back gate electrode in the cavity and hole having surfaces covered with the back gate insulating film;
• forming a front gate insulating film in a region on the semiconductor substrate in which a gate electrode of the MISFET is to be formed;
• forming a front gate electrode on the front gate insulating film, the front gate electrode having a different work function from that of the back gate electrode;
• selectively implanting impurities into portions of the semiconductor substrate which are not covered with the front gate electrode;
• partially etching the front gate electrode and front gate insulating film, to form a contact hole connected to the back gate electrode;
• and
• forming metal or metal silicide electrodes in the contact hole and on the front gate electrode.