Patent ID: 8354723

Claim:
An electro-static discharge protection device comprising: a substrate; a gate electrode formed over the substrate; a first diffusion region of a first conductivity type and a second diffusion region of the first conductivity type formed in the substrate with the gate electrode located in between; a first silicide layer formed in a local region in a surface of the first diffusion region, the first silicide layer being electrically coupled to an electrode pad; a silicide block region serving as a ballast resistor formed in the surface of the first diffusion region between the gate electrode and the first silicide layer; and a third diffusion region formed below the first silicide layer and at a position corresponding to the first silicide layer to partially overlap a lower end of the first diffusion region, wherein: the third diffusion region and the first silicide layer have substantially the same shapes and dimensions in a lateral direction; the third diffusion region and a portion below the gate electrode located at the substantially same depth as the third diffusion region contain impurities of a second conductivity type that differs from the first conductivity type; and the third diffusion region has an impurity concentration higher than that of the portion below the gate electrode located at the substantially same depth; wherein a pn junction surface of the first diffusion region of the first conductivity type and the substrate of the second conductivity type is formed below and corresponding to a substantial part of the silicide block region, and a diffusion region containing impurities of the second conductivity type with an impurity concentration higher than that of the portion below the gate electrode located at the substantially same depth is not formed on the pn junction surface below the silicide block region.