Semiconductor memory device having an electrically floating body transistor

1. A semiconductor memory cell formed in a semiconductor, the semiconductor memory cell comprising:

a floating body region defining at least a portion of a surface of the semiconductor memory cell, the floating body region having a first conductivity type;

a buried region located within the semiconductor memory cell and located adjacent to the floating body region, wherein the buried region has a second conductivity type,

wherein the floating body region is bounded on the sides by at least a first insulating region having a first thickness and a second insulating region having a second thickness, wherein the second thickness is greater than the first thickness; and

a gate region above the floating body region and the second insulating region and is insulated from the floating body region by an insulating layer.

2. The semiconductor memory cell of claim 1 , wherein said memory cell further comprises a bit line region at said surface, the bit line region having the second conductivity type.

3. The semiconductor memory cell of claim 1 , further comprising a first well region of the first conductivity type beneath the buried region.

4. The semiconductor memory cell of claim 1 , wherein said buried region is adapted to receive electrical signals of different amplitude or polarity, and wherein said electrical signals depend on an operation of said semiconductor memory cell.

5. The semiconductor memory cell of claim 2 , further comprising a single shared contact through which bit line regions of adjacent memory cells are coupled.

6. The semiconductor memory cell of claim 2 , further comprising a common region through which bit line regions of adjacent cells are coupled, the common region having the second conductivity type.

7. An array of memory cells formed in a semiconductor, the array comprising:

a plurality of memory cells arranged in a plurality of rows and a plurality of columns, wherein the rows of memory cells define a first direction and the columns of memory cells define a second direction, and each of said memory cells comprising:

a floating body region defining at least a portion of a surface of the memory cell, the floating body region having a first conductivity type;

a buried region located beneath the surface of the memory cell, the buried region having a second conductivity type; and

a gate region above the floating body region, where the gate region overlays two floating body regions in the first direction.

8. The array of semiconductor memory cells of claim 7 , wherein each of said semiconductor memory cells further comprises a bit line region located in the floating body region and substantially exposed at said surface, the bit line region having the second conductivity type.

9. The array of semiconductor memory cells of claim 7 , further comprising a plurality of source lines crossing the array in a first direction beneath said surface, wherein the plurality of source lines are coupled to said buried regions.

10. The array of semiconductor memory cells of claim 8 , further comprising a plurality of bit lines crossing the array in a second direction substantially orthogonal to the first direction, wherein the plurality of bit lines are coupled at said surface to said bit line regions.

11. The array of semiconductor memory cells of claim 7 , further comprising a plurality of word lines crossing the array in a first direction above said surface, wherein the plurality of word lines are coupled to said gate regions.

12. The array of semiconductor memory cells of claim 7 , further comprising a first well region of the first conductivity type beneath the buried region.

13. An array of memory cells formed in a semiconductor, the array comprising:

a plurality of semiconductor memory cells arranged in a matrix of rows and a plurality of columns wherein the rows of memory cells define a first direction and the columns of memory cells define a second direction, and each of said memory cells comprising:

a bipolar device having a floating base region, a first region, a second region, and a gate region wherein:

a state of said semiconductor memory cell is stored in said floating base region;

said first region is located at the surface of said floating base region;

said second region is located below said floating base region,

said second region is commonly connected to at least two of said semiconductor memory cells in said matrix; and

said gate region overlays two of said semiconductor memory cells along the column direction.

14. The array of semiconductor memory cells of claim 13 , further comprising a plurality of source lines crossing the array in a first direction beneath said surface, wherein the plurality of source lines are coupled to said second regions.

15. The array of semiconductor memory cells of claim 13 , further comprising a plurality of bit lines crossing the array in a second direction substantially orthogonal to the first direction, wherein the plurality of bit lines are coupled at said surface to said first regions.

16. The array of semiconductor memory cells of claim 13 , further comprising a plurality of word lines crossing the array in a first direction above said surface, wherein the plurality of word lines are coupled to said gate regions.

17. The array of semiconductor memory cells of claim 13 , further comprising a first well region of a first conductivity type beneath the buried region.

18. The array of semiconductor memory cells of claim 13 , wherein each of said second regions is adapted to receive electrical signals of different amplitude or polarity, wherein the electrical signals depend on an operation of each of said memory cells.

19. The array of semiconductor memory cells of claim 18 , wherein said electrical signal applied to said second region comprises a pulse.

20. The array of semiconductor memory cells of claim 18 , wherein said electrical signal applied to said second region comprises a constant amplitude level.