Semiconductor device and manufacturing method thereof

A semiconductor device provided with a MISFET having:

• a silicon substrate;
• a gate insulating film formed over a main surface of said silicon substrate;
• and
• a gate electrode formed over said gate insulating film,
• wherein said gate insulating film includes a first insulating film formed over said silicon substrate and a metal silicate layer formed over said first insulating film,
• wherein said metal silicate layer is composed of a plurality of silicon oxide layers alternatingly laminated with a plurality of metal oxide layers, each of the plurality of silicon oxide layers being laminated so as to be adjacent to at least one corresponding metal oxide layer,
• wherein one of said metal oxide layers formed closest to said gate electrode is thicker than another one of said metal oxide layers formed closest to said silicon substrate,
• wherein a concentration of silicon in said metal silicate layer is distributed to become higher on a silicon-substrate side than on a gate-electrode side,
• wherein a concentration of metal in said metal silicate layer is distributed to become lower on the silicon-substrate side than on the gate-electrode side, and
• wherein an Equivalent Oxide Thickness (EOT) of said gate insulating film is 1.0 nm or less.