Semiconductor device including capacitorless RAM

1. A semiconductor device comprising:

a field effect transistor having a floating body structure, and

an insulating layer underlying said field effect transistor,

wherein said field effect transistor comprises:

a first region comprising a first semiconductor having a given band gap;

a second region comprising a second semiconductor having a larger band gap than that of the first semiconductor; and

wherein a channel body region of said field effect transistor is disposed in said first region, said first region in said channel body region extending to said insulating layer.

2. The semiconductor device according to claim 1 , wherein the field effect transistor comprises:

the channel body region;

a source region;

a drain region;

a contact region electrically connected to said source or said drain region; and

wherein said second region comprising said second semiconductor is disposed between said channel body region and said contact region.

3. The semiconductor device according to claim 2 , wherein said channel body region of said field effect transistor is electrically isolated from a substrate by use of an insulating material.

4. The semiconductor device according to claim 1 , wherein said first semiconductor comprises SiGe and said second semiconductor comprises Si.

5. The semiconductor device according to claim 1 , wherein a first layer comprising said first semiconductor and a second layer comprising said second semiconductor are stacked in an area partitioned by an insulating film, and a gate electrode is located over a region where said first layer comprising said first semiconductor, a part of said second layer being absent comprising said second semiconductor, a gate insulating film being arranged between the gate electrode and said region.

6. The semiconductor device according to claim 1 , wherein a first layer comprising said first semiconductor is formed in the area partitioned by the insulating film, and said second semiconductor is buried and formed in a part of the source and drain regions of the field effect transistor, disposed in the first layer comprising said first semiconductor.

7. The semiconductor device according to claim 1 , wherein a second layer comprising said second semiconductor is formed in the area partitioned by the isolation insulating film, and a channel body region comprising said first semiconductor having a doping element different from an element constituting said second semiconductor.

8. The semiconductor device according to claim 1 , wherein a first layer comprising said first semiconductor is formed in the area partitioned by an element isolation insulating film, and a build-up structure of said second semiconductor is constructed on a source and drain regions of said field effect transistor, disposed in the first layer comprising said first semiconductor.

9. The semiconductor device according to claim 8 , wherein the build-up structure of said second semiconductor is formed as a lower part structure of a contact region.

10. The semiconductor device according to claim 1 , wherein at least a part of a gate electrode of the field effect transistor is disposed within a recess which reaches said first semiconductor.

11. The semiconductor device according to claim 1 , wherein said field effect transistor comprises a gate electrode which comprises polycrystalline silicon and refractory metal element.

12. The semiconductor device according to claim 1 , wherein the field effect transistor comprises:

the channel body region;

a gate electrode;

a source region;

a drain region; and

wherein a silicide layer is disposed on the gate electrode, the source region and the drain region.

13. The semiconductor device according to claim 12 , wherein said silicide layer is a cobalt silicide layer.

14. A data processing system comprising:

a DATA processor;

an I/O device;

a storage device;

a RAM;

wherein said RAM comprises the device of claim 1 .

15. A semiconductor device comprising:

a field effect transistor having a floating body structure, comprising:

a first region comprising a first semiconductor having a given band gap;

a second region comprising a second semiconductor having a larger band gap than that of the first semiconductor;

a channel body region being disposed in said first region;

a source region;

a drain region, and

wherein each of said source and drain region has a high density dopant region and a low density dopant region; and

each said low density dopant region is disposed at least between said channel body region and said high density dopant region of said source or said drain region;

said semiconductor device further comprising an insulating layer underlying said field effect transistor.

16. A semiconductor device comprising:

a field effect transistor having a floating body structure, wherein said field effect transistor comprises:

a first region comprising a first semiconductor having a given band gap;

a second region comprising a second semiconductor having a larger band gap than that of the first semiconductor; and

wherein a channel body region of said field effect transistor is disposed in said first region,

wherein the field effect transistor including the floating body structure is arranged at respective intersections of a plurality of word lines and a plurality of bit lines, and one of the source and drain regions of the field effect transistor is electrically connected to the bit line, and the other of the source and drain regions of the field effect transistor is electrically connected to a source line, and the plurality of bit lines are connected via a selecting switch to a sense amplifier, and the sense amplifier is connected to a line to supply a current having an intermediate value between ON current and OFF current of the field effect transistor.

17. The semiconductor device according to claim 16 , wherein the device is disposed in a package.

18. A memory card device, wherein the memory card device having mounted therein a chip comprising the semiconductor device according to claim 16 .

19. A memory module device, wherein the memory module device comprises the semiconductor device according to claim 16 .

20. The memory module device according to claim 19 , further comprising: a memory controller device.