Solid state imaging device and method for fabricating the same

A solid state imaging device comprising:

• a semiconductor substrate;
• a first oxide film and a first nitride film formed over the semiconductor substrate so as to be stacked in this order;
• a plurality of first gate electrodes arranged on the first nitride film so as to be spaced apart from one another with a predetermined distance therebetween;
• a second oxide film formed so as to cover upper part and side walls of each said first gate electrode;
• a second nitride film formed so as to cover the second oxide film and part of the first nitride film located between the first gate electrodes;
• a plurality of second gate electrodes formed on at least part of the second nitride film located between adjacent two of the first gate electrodes, a third oxide film formed so as to cover upper part and side walls of each said second gate electrode;
• a third nitride film formed so as to cover the third oxide film and part of the second nitride film located between the second gate electrodes;
• and
• a plurality of third gate electrodes formed on at least part of the third nitride film located between adjacent two of the second gate electrodes,
• wherein each said second gate electrode is separated from an associated one of the first gate electrodes by the second oxide film and the second nitride film and is separated from the semiconductor substrate by the first oxide film, the first nitride film and the second nitride film, and
• wherein each said third gate electrode is separated from an associated one of the second gate electrodes by the third oxide film and the third nitride film and separated from the semiconductor substrate by the first oxide film, the first nitride film, the second nitride film and the third nitride film.

A method for fabricating a solid state imaging device, the method comprising:

• a first step of forming a first oxide film and a first nitride film over a semiconductor substrate so that the first oxide film and the first nitride film are stacked in this order;
• a second step of forming, on the first nitride film, a plurality of first gate electrodes so that the first gate electrodes are arranged so as to be spaced apart from one another with a predetermined distance therebetween;
• a third step of forming a second oxide film so that the second oxide film covers upper part and side walls of each said first gate electrode;
• a fourth step of forming a second nitride film so that the second nitride film covers the second oxide film and part of the first nitride film located between the first gate electrodes;
• and
• a fifth step of forming a plurality of second gate electrodes on at least part of the second nitride film located between adjacent two of the first gate electrodes.

A method for fabricating a solid state imaging device, the method comprising:

• a first step of forming a first oxide film and a first nitride film over a semiconductor substrate so that the first oxide film and the first nitride film are stacked in this order;
• a second step of forming, on the first nitride film, a plurality of first gate electrodes so that the first gate electrodes are arranged so as to be spaced apart from one another with a predetermined distance therebetween;
• a third step of forming a second oxide film so that the second oxide film covers upper part and side walls of each said first gate electrode;
• a fourth step of forming a second nitride film so that the second nitride film covers the second oxide film and part of the first nitride film located between the first gate electrodes;
• a fifth step of forming a plurality of second gate electrodes on at least part of the second nitride film located between adjacent two of the first gate electrodes;
• a sixth step of forming a third oxide film so that the third oxide film covers upper part and side walls of each said second gate electrode;
• a seventh step of forming a third nitride film so that the third nitride film covers the third oxide film and part of the second nitride film located between the second gate electrodes;
• and
• an eighth step of forming a plurality of third gate electrodes on at least part of the third nitride film located between adjacent two of the second gate electrodes.