A semiconductor device comprising: a first transistor that includes a first primary terminal, a second primary terminal, and a first control terminal; a second transistor that includes a third primary terminal, a fourth primary terminal, a second control terminal and a back gate electrode, wherein the third primary terminal includes a first diffusion region of a first-conductivity-type arranged in a first well region of the first conductivity type, the fourth primary terminal includes a second diffusion region of the first conductivity-type arranged in a second well region of a second conductivity type, the back gate electrode includes a third diffusion region of the second conductivity type arranged in the second well region, the first well region and the second well region are arranged on a buried layer of the first conductivity type arranged on a semiconductor region (200, 301) of the second conductivity type; a first resistive element; a capacitive element (Ca) which includes a first terminal and a second terminal; a third transistor which includes a fifth primary terminal, a sixth primary terminal, and a third control terminal; and a driving unit, wherein the first primary terminal, the third primary terminal, and the first terminal are connected to a first voltage line, the second primary terminal, one terminal of the first resistive element, and the sixth primary terminal are connected to a second voltage line, the first control terminal, the second control terminal, the back gate electrode, the fourth primary terminal, and the other terminal of the first resistive element are connected to each other so as to form one node, the fifth primary terminal is connected to the second terminal, a potential change in the third primary terminal is transmitted to the first control terminal via capacitive coupling between the third primary terminal and the one node, a transmitted potential change at the first control terminal turns on the first transistor, the driving unit is configured to cause an insulation breakdown of the capacitive element (Ca) by supplying a control signal to the third control terminal, when a surge voltage is applied to the first voltage line, the first transistor turns on before the insulation breakdown of the capacitive element (Ca) occurs; and each of the first transistor and the second transistor comprises a Double-Diffused MOS, DMOS, transistor or a Laterally Diffused MOS, LDMOS, transistor. a first transistor that includes a first primary terminal, a second primary terminal, and a first control terminal; a second transistor that includes a third primary terminal, a fourth primary terminal, a second control terminal and a back gate electrode, wherein the third primary terminal includes a first diffusion region of a first-conductivity-type arranged in a first well region of the first conductivity type, the fourth primary terminal includes a second diffusion region of the first conductivity-type arranged in a second well region of a second conductivity type, the back gate electrode includes a third diffusion region of the second conductivity type arranged in the second well region, the first well region and the second well region are arranged on a buried layer of the first conductivity type arranged on a semiconductor region (200, 301) of the second conductivity type; a first resistive element; a capacitive element (Ca) which includes a first terminal and a second terminal; a third transistor which includes a fifth primary terminal, a sixth primary terminal, and a third control terminal; and a driving unit, wherein the first primary terminal, the third primary terminal, and the first terminal are connected to a first voltage line, the second primary terminal, one terminal of the first resistive element, and the sixth primary terminal are connected to a second voltage line, the first control terminal, the second control terminal, the back gate electrode, the fourth primary terminal, and the other terminal of the first resistive element are connected to each other so as to form one node, the fifth primary terminal is connected to the second terminal, a potential change in the third primary terminal is transmitted to the first control terminal via capacitive coupling between the third primary terminal and the one node, a transmitted potential change at the first control terminal turns on the first transistor, the driving unit is configured to cause an insulation breakdown of the capacitive element (Ca) by supplying a control signal to the third control terminal, when a surge voltage is applied to the first voltage line, the first transistor turns on before the insulation breakdown of the capacitive element (Ca) occurs; and each of the first transistor and the second transistor comprises a Double-Diffused MOS, DMOS, transistor or a Laterally Diffused MOS, LDMOS, transistor.