A semiconductor device includes a high breakdown voltage, high Gm first transistor and a low breakdown voltage, low Gm second transistor connected in series between first and second nodes, and a low breakdown voltage, high Gm third transistor connected to the second transistor in parallel. When the second transistor is turned on, the first transistor turns on, and furthermore, when the third transistor is turned on, an electrically conducting state is established between the first and second nodes. The second, low breakdown voltage transistor is turned on to turn on the first, high breakdown voltage transistor, and a turn-on time with only limited variation can be achieved.