Patent ID: 7439573

Claim:
A semiconductor device comprising: a first transistor having a composite gate structure containing a lamination of a first polycrystalline silicon film, an interlayer insulating film, and a second polycrystalline silicon film; and a second transistor having a single gate structure containing a lamination of a third polycrystalline silicon film and a fourth polycrystalline silicon film: wherein said first polycrystalline silicon film and said third polycrystalline silicon film have substantially the same thickness, and said first polycrystalline silicon film and said third polycrystalline silicon film have different impurity concentrations independently controlled of each other; and said second polycrystalline silicon film and said fourth polycrystalline silicon film have substantially the same thickness, and said second polycrystalline silicon film, said fourth polycrystalline silicon film, and also said third polycrystalline silicon film have substantially the same impurity concentration.