Semiconductor device

A semiconductor device, comprising:

• a first pad configured to input and output a signal;
• a second pad configured to be supplied with a reference voltage;
• an NPN transistor including a first collector, a first emitter, and a first base, the first collector connected to the first pad and the first emitter connected to the second pad;
• a PNP transistor including a second emitter, a second collector, and a second base, the second emitter connected to the first pad, the second collector connected to the second pad and the first base, and the second base connected to the first collector;
• an NMOS transistor including a drain, a source, and a gate, the drain connected to the first collector, the source connected to the second pad, and the gate connected to the source or the drain;
• and
• a first diode including an anode and a cathode, the anode connected to the drain, and the cathode connected to the first collector and the second base.

A semiconductor device, comprising:

• a first well region and a second well region isolated from each other by a first device isolation film;
• an NPN transistor provided by a first collector region and a first emitter region, the first collector region being formed in the first well region and including first conductivity-type impurities, and the first emitter region being formed in the second well region and including the first conductivity-type impurities;
• a PNP transistor provided by a second emitter region and a second collector region, the second emitter region being formed in the first well region and including second conductivity-type impurities different from the first conductivity-type impurities, and the second collector region being formed in the second well region and including the second conductivity-type impurities;
• and
• an NMOS transistor including a source region, a drain region, and a gate structure, the source region and the drain region being formed in the second well region and including the first conductivity-type impurities, and the gate structure being disposed between the source region and the drain region,
• wherein the source region and the drain region are isolated from each other by the first emitter region and a second device isolation film.