Capacitor-less memory cells and cell arrays
A capacitor-less memory cell, memory device, system and process of forming the capacitor-less memory cell includes forming the memory cell in an active area of a substantially physically isolated portion of the bulk semiconductor substrate. A pass transistor is formed on the active area for coupling with a word line. The capacitor-less memory cell further includes a read/write enable transistor vertically configured along at least one vertical side of the active area and operable during a reading of a logic state with the logic state being stored as charge in a floating body area of the active area, causing different determinable threshold voltages for the pass transistor.
1. A capacitor-less memory cell, comprising:
an active area formed from a bulk semiconductor substrate;
a pass transistor formed on the active area, the pass transistor including a source region, a drain region for coupling with a digit line and a gate for coupling with a word line; and
a read/write enable transistor including a gate, a source region, and a drain region commonly shared with the source region of the pass transistor, the read/write enable transistor vertically configured along at least one vertical side of the active area and operable during a reading of a logic state, the logic state being storable as charge in a floating body area of the active area to cause different determinable threshold voltages for the pass transistor, wherein at least a portion of the active area is at least substantially physically isolated from the bulk semiconductor substrate by at least one material layer and the gate of the read/write enable transistor extending horizontally to be between the at least a portion of the active area and the source region of the read/write enable transistor in a vertical plane.
2. The capacitor-less memory cell of claim 1 , wherein the active area remains physically integrally connected with the bulk semiconductor substrate through a stem portion of the bulk semiconductor substrate, wherein the stem portion has a width that is narrower than a width of the active area.
3. The capacitor-less memory cell of claim 2 , wherein at least a portion of the gate of the read/write enable transistor is formed along at least one side of the stem portion connecting the active area and the bulk semiconductor substrate.
4. The capacitor-less memory cell of claim 3 , further comprising isolating oxide extending between at least another portion of the active area and the bulk semiconductor substrate on at least another one side of the stem portion.
5. The capacitor-less memory cell of claim 3 , wherein the source region of the read/write enable transistor is formed in the bulk semiconductor substrate.
6. The capacitor-less memory cell of claim 5 , wherein the source region of the read/write enable transistor is formed under the stem portion in the bulk semiconductor substrate.
7. The capacitor-less memory cell of claim 1 , wherein the commonly shared source region of the pass transistor and the drain region of the read/write enable transistor extends through a thickness of the a portion of the active area that is at least substantially physically isolated from the bulk semiconductor substrate.
8. The capacitor-less memory cell of claim 1 , wherein the floating body area of the active area is configured to be more negatively charged to represent a first logic state and the floating body area is configured to be less negatively charged to represent a second logic state.
9. An array of capacitor-less memory cells, comprising:
a plurality of active areas formed from a bulk semiconductor substrate;
a respective plurality of pass transistors formed on the respective plurality of active areas, each of the pass transistors including a source region, a drain region for coupling with a digit line and a gate for coupling with a word line; and
a respective plurality of read/write enable transistors each including a gate, a source region, and a drain region commonly shared with the source region of the pass transistor, each of the read/write enable transistors vertically configured along at least one vertical side of the respective active area and operable during a reading of a logic state, the logic state being storable as charge in a floating body area of the active area to cause different determinable threshold voltages for the pass transistor, wherein at least a portion of each of the plurality of active areas is at least substantially physically isolated from the bulk semiconductor substrate by at least one material layer and the gates of the respective plurality of read/write enable transistors extending horizontally to be between the at least a portion of each of the plurality of active areas and the source region of the respective plurality of read/write enable transistors in a vertical plane.
10. The array of capacitor-less memory cells of claim 9 , wherein each of the plurality of active areas remain physically integrally connected with the bulk semiconductor substrate through respective stem portions of the bulk semiconductor substrate, wherein the respective stem portions have widths that are narrower than a width of a corresponding active area of the plurality.
11. The array of capacitor-less memory cells of claim 10 , wherein at least a portion of the gate of each of the respective plurality of read/write enable transistors is formed along at least one side of the respective stem portions connecting each of the plurality of active areas and the bulk semiconductor substrate.
12. The array of capacitor-less memory cells of claim 11 , further comprising isolating oxide between at least another one side of the respective stem portions and the bulk semiconductor substrate.
13. The array of capacitor-less memory cells of claim 11 , wherein the source region of each of the respective plurality of read/write enable transistors is formed in the bulk semiconductor substrate.
14. The array of capacitor-less memory cells of claim 13 , wherein the source region of each of the respective plurality of read/write enable transistors is formed under the respective stem portions in the bulk semiconductor substrate.
15. The array of capacitor-less memory cells of claim 9 , wherein the commonly shared source region of each of the respective plurality of pass transistors and the drain region of each of the respective plurality of read/write enable transistors substantially extends through a thickness of at least a portion of each of the plurality of active areas that is at least substantially physically isolated from the bulk semiconductor substrate.
16. The array of capacitor-less memory cells of claim 9 , wherein the floating body area of each of the plurality of active areas is configured to be more negatively charged to represent a first logic state and the floating body area is configured to be less negatively charged to represent a second logic state.
17. The array of capacitor-less memory cells of claim 9 , further comprising addressing and sensing circuitry to determine the logic states based upon the presence or absence of current flow from each of the plurality of capacitor-less memory cells.
18. The array of capacitor-less memory cells of claim 17 , wherein the current flow from each of the plurality of capacitor-less memory cells is responsive to an amount of charge stored in a floating body area of each of the plurality of active areas to cause the different determinable threshold voltages of each of the respective plurality of pass transistors.