Semiconductor device having SOI structure and method for fabricating the same

摘要

A pn diode as an electrostatic discharge protection element of a MOSFET in a semiconductor device having an SOI structure to enable large current to flow is disclosed. N+ layers and p+ layers are formed on a surface of an element-isolation region isolated from another element region by dielectrics, and a polycrystalline silicon layer is formed by burying under these. Accordingly, the n+ layer and p+ layer and the n+ layer and p+ layer are respectively connected electrically via the polycrystalline silicon layer, structuring pn diodes. Consequently, the respective pn diodes become vertical pn junctions and it becomes possible to allow large current flow. Additionally, a MOSFET is formed on the dielectric in another element region, and a pn diode functions as an electrostatic discharge protection element of this MOSFET.