Solid-state imaging device and method of its production

A method for producing a solid-state image pickup device comprising:

• a charge transfer portion for transferring an electric charge produced in a light receiving portion through photoelectric conversion from an incident light to said electric charge, and
• an output amplifier portion for detecting said electric charge to issue a signal;
• wherein said charge transfer portion is provided with a first gate insulation film having a sufficient film thickness to keep a predetermined transfer efficiency, and
• said output amplifier portion is provided with a second gate insulation film having a film thickness suitable for obtaining a predetermined mutual conductance capable of increasing the gain of said output amplifier portion;
• the method comprising the steps of:
• forming an insulation film, in which a multilayer film is formed by stacking a thermal oxidation film, a nitride film, and a first Chemical Vapor Deposition (“CVD”) oxidation film together in the mentioned order in a region where said charge transfer portion and said output amplifier portion are formed on a semiconductor substrate;
• forming a first layer charge transfer electrode in a region where said charge transfer portion is formed;
• forming a second CVD oxidation film after all of said first CVD oxidation film, except said first CVD oxidation film immediately underneath said first layer charge transfer electrode, is removed;
• oxidizing said first layer charge transfer electrode to increase said second CVD oxidation film in film thickness;
• removing said multilayer film at said region where said output amplifier portion is formed;
• forming an oxide film serving as a gate insulation film in said region where said output amplifier portion is formed, and
• simultaneously again oxidizing said first layer charge transfer electrode to increase further said second CVD oxidation film in film thickness;
• and
• forming a second layer charge transfer electrode through both said multilayer film and said second CVD oxidation film in said region where said charge transfer portion is formed, and simultaneously forming a gate electrode in said region where said output amplifier portion is formed.