Abstract: A second conduction-type MIS transistor in which a source is coupled to a second power source over the surface of a first conduction-type well and a drain is coupled to the open-drain signal terminal is provided. A second conduction-type first region is provided at both sides of the MIS transistor in parallel with a direction where the electric current of the MIS transistor flows and coupled to the open-drain signal terminal. The whole these components are surrounded by a first conduction-type guard ring coupled to the second power source and the outside surrounded by the first conduction-type guard ring is further surrounded by a second conduction-type guard ring coupled to a first power source. Thereby, the semiconductor device is capable of achieving ESD protection of an open-drain signal terminal having a small area and not providing a protection element between power source terminals.

Abstract: A second conduction-type MIS transistor in which a source is coupled to a second power source over the surface of a first conduction-type well and a drain is coupled to the open-drain signal terminal is provided. A second conduction-type first region is provided at both sides of the MIS transistor in parallel with a direction where the electric current of the MIS transistor flows and coupled to the open-drain signal terminal. The whole these components are surrounded by a first conduction-type guard ring coupled to the second power source and the outside surrounded by the first conduction-type guard ring is further surrounded by a second conduction-type guard ring coupled to a first power source. Thereby, the semiconductor device is capable of achieving ESD protection of an open-drain signal terminal having a small area and not providing a protection element between power source terminals.

Abstract: A semiconductor device includes a first circuit block powered by voltages at first and second power supply terminals, a second circuit block powered by voltages at third and fourth power supply terminals, a first ESD (electrostatic discharge) protection circuit including a first field effect transistor having a source, a drain, and a gate, where the gate and one of the source and the drain are connected to the first power supply terminal, the other of the source and the drain is connected to the third power supply terminal, and a first back gate potential adjusting circuit adapted to adjust a potential at a back gate of the first field effect transistor. The first field effect transistor includes a first conductivity type transistor formed in a first well of a second conductivity type serving as the back gate of the first field effect transistor.

Abstract: A semiconductor device includes a first circuit block powered by voltages at first and second power supply terminals, a second circuit block powered by voltages at third and fourth power supply terminals, a first ESD (electrostatic discharge) protection circuit including a first field effect transistor having a source, a drain, and a gate, where the gate and one of the source and the drain are connected to the first power supply terminal, the other of the source and the drain is connected to the third power supply terminal, and a first back gate potential adjusting circuit adapted to adjust a potential at a back gate of the first field effect transistor. The first field effect transistor includes a first conductivity type transistor formed in a first well of a second conductivity type serving as the back gate of the first field effect transistor.

Abstract: In a semiconductor device including two circuit blocks, an ESD protection circuit between power supply terminals (or ground terminals) of the two circuit blocks having the same voltage level as each other is constructed by at least one diode-connected field effect transistor whose back gate potential is adjusted by a back gate potential adjusting circuit. As a result, the absolute value of the threshold voltage and the ON resistance of the ESD protection circuit can be changed in accordance with whether the operation mode is an ESD protection operation mode or a usual operation mode.

Abstract: In a semiconductor device including two circuit blocks, an ESD protection circuit between power supply terminals (or ground terminals) of the two circuit blocks having the same voltage level as each other is constructed by at least one diode-connected field effect transistor whose back gate potential is adjusted by a back gate potential adjusting circuit. As a result, the absolute value of the threshold voltage and the ON resistance of the ESD protection circuit can be changed in accordance with whether the operation mode is an ESD protection operation mode or a usual operation mode.