US Patent 9012997 Semiconductor device including ESD protection device

A semiconductor device includes a semiconductor-on-insulator (SOI) substrate having a bulk substrate layer, an active semiconductor layer and a buried insulator layer disposed between the bulk substrate layer and the active semiconductor layer. A trench is formed through the SOI substrate to expose the bulk substrate layer. A doped well is formed in an upper region of the bulk substrate layer adjacent trench. The semiconductor device further includes a first doped region different from the doped well that is formed in the trench.