Semiconductor device and manufacturing method thereof

A semiconductor device comprising:

• a recessed channel transistor including a trench formed in a semiconductor substrate;
• a gate electrode formed in the trench with a gate dielectric film therebetween, at least a part of the gate electrode extending above the semiconductor substrate;
• a diffusion layer region arranged in the semiconductor substrate near the gate electrode with the gate dielectric film therebetween;
• and a source electrode and a drain electrode that contact the diffusion layer region;
• a gate electrode extension part that is made of a conductive material and is laminated on the gate electrode so as to extend the gate electrode;
• a protective dielectric film that covers the semiconductor substrate around the gate electrode and surrounds a side face of the gate electrode that protrude from the trench;
• and
• an inter-layer dielectric film formed over the protective dielectric film.

A semiconductor device comprising:

• a transistor including a protective dielectric film formed on a semiconductor substrate;
• a trench formed in the protective dielectric film so as to reach the semiconductor substrate;
• a gate electrode formed in the trench with a gate dielectric film therebetween;
• a diffusion layer region arranged in the semiconductor substrate near the gate electrode with the gate dielectric film therebetween;
• and a source electrode and a drain electrode that contact the diffusion layer region;
• a gate electrode extension part made of a conductive material and laminated on the gate electrode so as to extend the gate electrode;
• a protective dielectric film that covers the semiconductor substrate around the gate electrode and surrounds a side face of the gate electrode;
• and
• an inter-layer dielectric film formed over the protective dielectric film.

A method of manufacturing a semiconductor device comprising:

• forming an element separating dielectric film in a semiconductor substrate where a diffusion layer region is formed;
• forming a protective dielectric film on the semiconductor substrate where the element separating dielectric film is formed;
• patterning the protective dielectric film, and forming a trench by etching the protective dielectric film and the semiconductor substrate while using the patterned protective dielectric film as a mask;
• forming a gate dielectric film along an inner face of the trench by performing an oxidation process to the diffusion layer region;
• forming a gate electrode on an inner side of the gate dielectric film by forming a polysilicon layer on the semiconductor substrate;
• flattening a surface of the semiconductor substrate by chemical mechanical polishing using the protective dielectric film as a stopper to align a top face of the protective dielectric film, a top face of the gate dielectric film, and a top face of the gate electrode in a single plane;
• forming a gate electrode extension part comprising a conductive material on the gate electrode;
• and
• forming a source electrode and a drain electrode that pass through the protective dielectric film and contact the diffusion layer region on a side of the gate dielectric film.

A method of manufacturing a semiconductor device comprising:

• forming an element separating dielectric film a semiconductor substrate where a diffusion layer region is formed;
• forming a protective dielectric film on the semiconductor substrate where the element separating dielectric film is formed;
• patterning the protective dielectric film and forming a trench that reaches a surface of the semiconductor substrate;
• forming, inside the trench, a gate dielectric film that reaches the semiconductor substrate and covers an inner face of the trench;
• forming a gate electrode on an inner side of the gate dielectric film by forming a polysilicon layer on the semiconductor substrate;
• flattening the surface of the semiconductor substrate by chemical mechanical polishing using the protective dielectric film as a stopper to align a top face of the protective dielectric film, a top face of the gate dielectric film, and a top face of the gate electrode in a single plane;
• forming a gate electrode extension part comprising a conductive material on the gate electrode;
• and
• forming a source electrode and a drain electrode that pass through the protective dielectric film and contact the diffusion layer region on a side of the gate dielectric film.