Semiconductor device and method for manufacturing thereof

A semiconductor device comprising:

• a first semiconductor domain and a second semiconductor domain isolated from each other by a field dielectric layer for device isolation formed selectively on a surface of a silicon semiconductor substrate;
• a first MOS (Metal Oxide Semiconductor) device using a nitrogen-containing silicon oxide film formed on a surface of the first semiconductor domain as a gate dielectric;
• and
• a second MOS device using an oxygen-containing silicon nitride film formed on a surface of the second semiconductor domain as a gate dielectric,
• wherein the nitrogen concentration in the nitrogen-containing silicon oxide film is maximum either at the surface of the silicon dioxide or at the boundary between the silicon dioxide and the silicon semiconductor substrate, and the oxygen concentration of the oxygen-containing silicon nitride film is minimum in an intermediate portion of the film between the boundary of the silicon nitride film and the silicon semiconductor substrate and the surface of the silicon nitride film.

A method for manufacturing a semiconductor device comprising the steps of:

• forming a first semiconductor domain and second semiconductor domain isolated from each other by forming a field dielectric layer for device isolation selectively on the surface of a silicon semiconductor substrate;
• depositing a first silicon dioxide on surfaces of the first semiconductor domain and the second semiconductor domain by chemical vapor deposition;
• removing the first silicon dioxide deposited on the surface of the second semiconductor domain for exposing the surface of the second semiconductor domain;
• forming a nitrogen-containing silicon oxide film in the first semiconductor domain and forming a silicon nitride film in the second semiconductor domain by nitriding the first silicon dioxide in the first semiconductor domain and the exposed surface of the second semiconductor domain;
• removing the nitrogen-containing silicon oxide film formed on the first semiconductor domain for exposing the surface of the first semiconductor domain;
• forming a second silicon dioxide in the first semiconductor domain and forming an oxygen-containing silicon nitride film in the second semiconductor domain by oxidizing the exposed surface of the first semiconductor domain and the silicon nitride film in the second semiconductor domain;
• and
• forming MOS (Metal Oxide Semiconductor) devices in the first semiconductor domain and the second semiconductor domain by using the second silicon dioxide and the oxygen-containing silicon nitride film as gate dielectrics, respectively.