| abstract |
Conventionally, the thicker the gate oxide film is, the sharper the substrate and the local thinning of the gate oxide film become, and the gate breakdown voltage at the shallow groove element isolation end is deteriorated. In the present invention, a bird's beak is provided at the end of the shallow groove element isolation structure GR0XI11 directly below the gate electrode POLY11 and in contact with the gate insulating film HOX1, and a thick gate insulating film HOX1 is formed first. As a result, it is possible to ensure normal gate breakdown voltage, good device isolation breakdown voltage and high integration of the MOS transistor at the same time. |