A semiconductor device in which only the trigger voltage can be controlled without change in the hold voltage. In the semiconductor device, a protection device includes a lower doped collector layer, a sinker layer, a highly-doped collector layer, an emitter layer, a highly-doped base layer, a base layer, a first conductivity type layer, and a second conductivity type layer. The second conductivity type layer is formed in the lower doped collector layer and located between the base layer and first conductivity type layer. The second conductivity type layer has a higher impurity concentration than the lower doped collector layer.