Patent ID: 7679148

Claim:
A semiconductor device comprising an insulating film structure which electrically insulates a conductive region from a silicon region, wherein said insulating film structure extends on said silicon region and under said conductive region, said insulating film structure further comprising at least one silicate region composed of a silicon oxide containing at least one metal element, wherein said insulating film structure comprises at least one silicon oxide region composed of a silicon oxide not containing said at least one metal element, at least one metal rich region having high concentration of said at least one metal element, and said at least one silicate region which is located between said silicon oxide region and said metal rich region and has lower concentration of said at least one metal element than that of said metal rich region, wherein said silicon oxide region is located on said silicon region, said silicate region being located on said silicon oxide region, said metal rich region being located on said silicate region, wherein said silicate region has composition modulation in which composition of said at least one metal element increases toward a surface of the device, and the composition of silicon decreases toward the surface of the device, and wherein a second silicate region further extends on said metal rich region, the second silicate region having composition modulation in which composition of said at least one metal element decreases upward, and the composition of silicon increases upward.