SEMICONDUCTOR DEVICE AND MANUFACTURING METHOD THEREFOR

摘要

PROBLEM TO BE SOLVED: To provide a semiconductor device having a low breakdown voltage transistor having a stable characteristic without diffusion of boron in a polycrystalline silicon film which becomes a gate electrode to a semiconductor substrate and a high breakdown voltage transistor, having a gate insulting film whose film thickness is controlled on the same substrate. SOLUTION: An oxynitirde film 5 is formed in a low breakdown voltage transistor LMOS region and an oxide film 7 which becomes the gate insulating film of high breakdown voltage transistor HMOS is formed through a thermal oxidation processing. At that time, a low breakdown voltage transistor LMOS region is oxidized simultaneously and a laminated film, which becomes the gate insulating film 8 of the low breakdown voltage transistor and is constituted of the oxide film and the oxynitride film is formed.