Semiconductor device and manufacturing method thereof

Abstract

A semiconductor device includes a silicon substrate, an SiO film, and a High-K film. The SiO film is first formed on the silicon substrate and then subjected to a nitridation process to obtain an SiON film from the SiO film. The nitridation process is performed such that nitrogen concentration in the SiO film decreases from an interface with the silicon substrate below and an interface with the High-K film above, and nitrogen having predetermined concentration or more is introduced in a thickness within a range of 0.2 nm to 1 nm from the interface with the silicon substrate. The SiON film is etched up to a depth to which nitrogen of the predetermined concentration or more is introduced. The High-K film is then formed on the SiON film.

1 .- 15 . (canceled) 
     
     
         16 . A semiconductor device comprising:
 a silicon substrate;   an element-isolation dielectric film formed on a surface of the silicon substrate;   a gate electrode formed on the silicon substrate surrounded by the element-isolation dielectric film via a high-dielectric-constant material film having a higher dielectric constant than that of silicon oxide;   a source/drain region formed on the surface of the silicon substrate around the gate electrode; and   an interface layer including silicon oxide-nitride film having a peak in a depth-direction distribution of nitrogen concentration near an interface with the silicon substrate, and having a thickness within 0.2 nanometer to 1 nanometer, between the silicon substrate and the high-dielectric-constant material film.   
     
     
         17 . The semiconductor device according to  claim 16 , wherein nitrogen concentration in the interface layer at an interface with the high-dielectric-constant material film is equal to or higher than 10 at %. 
     
     
         18 . The semiconductor device according to  claim 17 , wherein nitrogen concentration in the interface layer near an interface with the silicon substrate is equal to or higher than 20 at %. 
     
     
         19 . The semiconductor device according to  claim 16 , wherein a corner of an upper part of a cross section of the silicon substrate in a direction perpendicular to an extension direction of the gate electrode in contact with the element-isolation dielectric film is round.