MOS semiconductor device with breakdown voltage performance and method for manufacturing the same

摘要

MOS semiconductor device including a substrate having source and drain regions laterally spaced from one another and a channel therebetween, a gate electrode over the channel and an oxide layer. The oxide layer includes a gate oxide layer between the gate electrode and the substrate, an oxide film having a having a thickness greater than a thickness of the gate oxide layer and a boundary oxide layer between the gate oxide layer and oxide film. The boundary oxide layer has a thickness between the thickness of the gate oxide layer and the thickness of the oxide film. The oxide film boundary oxide layer are formed by selective oxidation before formation of the gate electrode. The gate electrode has end portions extending over a portion of the oxide film while receiving no distortion from the boundary oxide layer to thereby improve breakdown voltage performance at the end portions of the gate electrode.