Abstract: An ESD protection semiconductor device includes a substrate, a buried layer buried in the substrate, a first well formed in the substrate, a first doped region formed in the first well, a second doped region formed in the first well and adjacent to the first doped region, a second well formed in the first well, and a third doped region formed in the second well. The buried layer, the first well, the first doped region, and the third doped region include a first conductivity type while the second doped region and the second well include a second conductivity type complementary to the first conductivity type. The second well is spaced apart from the first doped region and the second doped region by the first well.