| 摘要 |
PURPOSE:To suppress a punch through effectively and to keep a parasitic resistance small by thinning a gate insulating film existing directly under a channel region and by sufficiently thickening an insulating film in contact with a source region and drain region. CONSTITUTION:There is formed an opening 12A corresponding to a part expected to form a channel region in a first silicon semiconductor substrate 11. When a thermal oxidation method is applied, a gate insulating film 13 composed of SiO2 is formed so that the thickness of the film in the opening 12A is e.g. 100(Angstrom ). Then, a polycrystalline silicon film is patterned so that a gate electrode 14 for applying a back gate bias voltage is formed. Subsequently, when a CVD method is applied, a layer insulating film 15 composed of SiO2 having a thickness of e.g. 1000(Angstrom ) is formed all over the surface. Further, the CVD method is applied so that a polycrystalline silicon film 16 having a thickness of e.g. 3000(Angstrom ) is formed all over the surface.
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