US Patent 7592684 Semiconductor device and method for manufacturing the same

A semiconductor device is provided in which high breakdown voltage transistors and low voltage driving transistors are formed on the same substrate. The device includes a semiconductor layer, first element isolation regions for defining a high breakdown voltage transistor forming region in the semiconductor layer, second element isolation regions including trench dielectric layers for defining a low voltage driving transistor forming region in the semiconductor layer, high breakdown voltage transistors formed in the high breakdown voltage transistor forming region, low voltage driving transistors formed in the low voltage driving transistor forming region, and offset dielectric layers for alleviating the electric field of the high breakdown voltage transistors formed in the high breakdown voltage transistor forming region, wherein upper ends of the offset dielectric layers are beak shaped.