Semiconductor integrated circuit device with MOSFET limiter circuit
Latchup is prevented from occurring accompanying increasingly finer geometries of a chip. NchMOSFET N 1 and PchMOSFET P 1 form a CMOS circuit including: NchMOSFET N 2 whose gate, drain and back gate are connected to back gate of N 1 and PchMOSFET P 2 whose gate, drain and back gate are connected to back gate of P 1 . Source of N 2 is connected to source of N 1 . Source of P 2 is connected to source of P 1 . N 2 is always connected between the grounded source of N 1 and the back gate of N 1 , while P 2 is connected between source of P 1 connected to a power supply and the back gate of P 1 . Each of N 2 and P 2 functions as a voltage limiting element (a limiter circuit).
1. A semiconductor integrated circuit device including a CMOS circuit, comprising:
a first MOSFET forming said CMOS circuit; and
a first limiter circuit connected between a back gate of said first MOSFET and a source of said first MOSFET, said first limiter circuit formed of a second MOSFET having a gate, a drain, and a back gate, each connected to the back gate of said first MOSFET,
wherein said second MOSFET has the same conductivity type as said first MOSFET and a source of said second MOSFET is connected to the source of said first MOSFET, and the back gates of the first and second MOSFETs are both connected to a first back bias supplying power supply line by way of a well region in which said first and second MOSFETs are formed.
2. The semiconductor integrated circuit device according to claim 1 , further comprising:
a third MOSFET forming said CMOS circuit, said third MOSFET having a conductivity type opposite to a conductivity type of said first MOSFET; and
a second limiter circuit connected between a back gate of said third MOSFET and a source of said third MOSFET, said second limiter circuit limiting a forward voltage at a pn junction formed between the back gate of said third MOSFET and the source of said third MOSFET so that a forward current at the pn junction is cut off.
3. The semiconductor integrated circuit device according to claim 2 , wherein said second limiter circuit is formed of a fourth MOSFET, said fourth MOSFET having the same conductivity type as said third MOSFET, and wherein a gate, a drain and a back gate of said fourth MOSFET are each connected to the back gate of said third MOSFET, and a source of said fourth MOSFET is connected to the source of said third MOSFET, and the back gates of the third and fourth MOSFETs are both connected to a second back bias supplying power supply line by way of another well region in which said third and fourth MOSFETs are formed.
4. A semiconductor integrated circuit device, comprising:
a CMOS circuit that comprises:
a well region of a first conductivity type formed in a band form in a substrate;
a well region of a second conductivity type formed in a band form in said substrate, said well region of the second conductivity type being arranged in parallel with and adjacent to said well region of the first conductivity type;
a first diffusion region of the first conductivity type formed in said well region of the first conductivity type and connected to a first back bias supplying power supply line that supplies a back bias to be supplied to said well region of the first conductivity type;
first and second power supply lines that supply power to said CMOS circuit; and
a MOSFET of the second conductivity type formed in said well of the first conductivity type, a gate and a drain of the MOSFET of the second conductivity type being connected to the well region of the first conductivity type through a second diffusion region of the first conductivity type formed in the well region, and a source of the MOSFET of the second conductivity type being connected to the first power supply line.