Patent ID: 7161198
Filing Date: 2007-01-09
Classification: H01L

Abstract:
1. A semiconductor device comprising: a semiconductor substrate; an epitaxial layer formed on the semiconductor substrate; a well region formed under a surface of the epitaxial layer; a field oxide film formed on the well region; a MOS transistor formed in the well region and having a source region, a gate region disposed adjacent the field oxide film, a first drain drift region disposed under the field oxide film, and a second drain drift region disposed under the first drain drift region; and a buried diffusion layer disposed in direct contact with the well region and formed between the semiconductor substrate and the epitaxial layer, the buried diffusion layer being disposed directly under the second drain drift region but not under the source region of the MOS transistor; wherein the semiconductor substrate and the epitaxial layer have a first conductivity type, the buried diffusion layer and the well region have a second conductivity type, and the second drain drift region has the same conductivity type as but a lower impurity concentration than the first drain drift region.