Semiconductor device with electrostatic protection device

1. A semiconductor device having an SOI (Silicon On Insulator) structure and comprising a P-channel FET and an N-channel FET which are formed on an insulating film, said semiconductor device comprising:

at least two of first, second, third and fourth PN-junction elements,

wherein said first PN-junction element is formed from a P-type semiconductor layer and an N-type semiconductor layer having the same impurity concentrations as those of source/drain regions of said P-channel FET and said N-channel FET, respectively,

wherein said second PN-junction element is formed from a P-type semiconductor layer and an N-type semiconductor layer having the same impurity concentrations as those of the source/drain region and a channel region in said P-channel FET, respectively,

wherein said third PN-junction element is formed from a P-type semiconductor layer and an N-type semiconductor layer having the same impurity concentrations as those of a channel region and the source/drain region in said N-channel FET, respectively,

wherein said fourth PN-junction element is formed from a P-type semiconductor layer and an N-type semiconductor layer having the same impurity concentrations as those of the channel regions of said N-channel FET and said P-channel FET, respectively, and

wherein said at least two PN-junction elements are connected in series in a forward bias between two different terminals to form an electrostatic protection device.

2. The semiconductor device according to claim 1 , wherein a junction plane of each of said first to fourth PN-junction elements is orthogonal to a plane of said insulating film.

3. The semiconductor device according to claim 1 , wherein a plurality of sets of said at least two PN-junction elements connected in series are connected in parallel.

4. The semiconductor device according to claim 1 , wherein a set of said two different terminals are one of a set of a power supply terminal and a ground line terminal, a set of an input/output signal terminal and said power supply terminal, a set of said input/output signal terminal and said ground line terminal, a set of an internal power supply terminal and said ground line terminal, and a set of an internal signal line terminal and said ground line terminal.

5. The semiconductor device according to claim 1 , wherein a summation of forward bias voltages corresponding to said at least two PN-junction elements between said two different terminals is larger than a power supply voltage or a signal voltage applied between said two different terminals.

6. The semiconductor device according to claim 1 , wherein said P-type semiconductor layer of one of said at least two PN-junction elements is connected to an N-type semiconductor layer of the other of said at least two PN-junction elements by a conductive wiring which extends in a direction orthogonal to a PN-junction plane of said one PN-junction element.

7. The semiconductor device according to claim 1 , wherein each of said first to fourth PN-junction elements has a non-implantation region between two semiconductor layers in which impurities are implanted, and a junction plane is formed in the non-implantation region through a thermal process.

8. The semiconductor device according to claim 1 , wherein each of said P-type FET and said N-type FET comprises source/drain regions of an LDD structure.

9. The semiconductor device according to claim 1 , wherein a PN-junction plane of each of said first to fourth PN-junction elements has a polygonal shape or a circular shape.

10. The semiconductor device according to claim 1 , wherein each of said first to fourth PN-junction elements has a semiconductor layer formed on said insulating film,

said semiconductor layer has a P-type impurity implantation region, an N-type impurity implantation region and a non-implantation region therebetween, and

a PN-junction of said PN-junction element is formed in said non-implantation region.

11. The semiconductor device according to claim 1 , wherein each of said P-type FET and said N-type FET of the SOI structure is a FinFET or a column-like MISFET, and

one of said P-type semiconductor layer and said N-type semiconductor layer includes a source/drain diffusion region of said FinFET or said column-like MISFET.

12. The semiconductor device according to claim 1 , wherein silicide layers are formed on predetermined areas of said P-type and N-type semiconductor layers.

13. The semiconductor device according to claim 1 , wherein said electrostatic protection device further comprises a-plurality of PN-junction elements of said first to fourth PN-junction elements, and

one of said plurality of PN-junction elements is selectively connected to said at least two PN-junctions by fuse elements or a wiring whose pattern is changed.

14. A-semiconductor device comprising a P-type FET and an N-type FET formed on an insulating film in an SOI structure,

wherein PN-junction elements having different forward bias voltages are formed through a P-type impurity implantation process and an N-type impurity implantation process, and

wherein at least two of said PN-junction elements are connected in series.

15. The semiconductor device according to claim 14 , wherein a P-type semiconductor layer of one of said at least two PN-junction elements is connected to an N-type semiconductor layer of the other of said at least two PN-junction elements by a conductive wiring which extends in a direction orthogonal to a PN-junction plane of said one PN-junction element.

16. The semiconductor device according to claim 14 , wherein each of said first to fourth PN-junction elements has a semiconductor layer formed on said insulating film,

said semiconductor layer has a P-type impurity implantation region, an N-type impurity implantation region and a non-implantation region therebetween, and

a PN-junction of said PN-junction element is formed in said non-implantation region.

17. The semiconductor device according to claim 14 , wherein each of said P-type FET and said N-type FET comprises source/drain regions of an LDD structure.

18. The semiconductor device according to claim 14 , wherein a PN-junction plane of each of said first to fourth PN-junction elements has a polygonal shape or a circular shape.

19. The semiconductor device according to claim 14 , wherein each of said first to fourth PN-junction elements has a semiconductor layer formed on said insulating film,

said semiconductor layer has a P-type impurity implantation region, an N-type impurity implantation region and a non-implantation region therebetween, and

a PN-junction of said PN-junction element is formed in said non-implantation region,

The said half conductor layer has the Anne dope area which doesn't pour N-type impurities and P-type impurities.

20. The semiconductor device according to claim 14 , wherein each of said P-type FET and said N-type FET of the SOI structure is a FinFET or a column-like MISFET, and

one of said P-type semiconductor layer and said N-type semiconductor layer includes a source/drain diffusion region of said FinFET or said column-like MISFET.