P-channel electrically alterable non-volatile memory cell
View Patent ↗A nonvolatile memory cell is provided. The memory cell comprises a storage transistor and an injector in a semiconductor substrate of a p-type conductivity. The injector comprises a first region of the p-type conductivity and a second region of an n-type conductivity. The storage transistor comprises a source, a drain, a channel, a charge storage region, and a control gate. The source and the drain have the p-type conductivity and are formed in a well of the n-type conductivity in the substrate with the channel of the well defined therebetween. The charge storage region is disposed over and insulated from the channel by a first insulator. The control gate is disposed over and insulated from the charge storage region by a second insulator. Further provided are methods operating the memory cell, including means for injecting electrons from the channel through the first insulator onto the charge storage region and means for injecting holes from the injector through the well through the channel through the first insulator onto the charge storage region.
1. An electrically erasable and programmable nonvolatile memory device comprising:
a substrate of semiconductor material of a p-type conductivity;
a well of an n-type conductivity in the substrate;
an injector having a first region of the p-type conductivity and a second region of the n-type conductivity; and
a storage transistor having a source and a drain of the p-type conductivity and formed in the well with a channel of the well defined therebetween, a charge storage region disposed over and insulated from the channel by a first insulator, and a control gate disposed over and insulated from the charge storage region by a second insulator.
2. The memory device of claim 1 , wherein the first region comprises the substrate.
3. The memory device of claim 1 , wherein the second region comprises the well.
4. The memory device of claim 1 , wherein the first region comprises a first buried well of the p-type conductivity having a doping level in the range between about 1×10 15 atoms/cm 3 to about 1×10 20 atoms/cm 3 .
5. The memory device of claim 1 , wherein the second region comprises a second buried well of the n-type conductivity having a doping level in the range between about 1×10 16 atoms/cm to about 5×10 19 atoms/cm 3 .
6. The memory device of claim 1 , wherein the first region comprises a semiconductor region of the p-type conductivity disposed adjacent to and isolated from the channel by an isolation region, and the second region comprises the well.
7. The memory device of claim 6 , wherein the isolation region comprises an oxide.
8. The memory device of claim 1 , wherein the charge storage region comprises polysilicon.
9. The memory device of claim 1 , wherein the charge storage region comprises a plurality of spaced-apart nano-crystals of a semiconductor material.
10. The memory device of claim 1 , wherein the charge storage region comprises a dielectric having a plurality of charge storing traps.
11. The memory device of claim 1 , further comprising:
means for injecting electrons from the channel through the first insulator onto the charge storage region; and
means for injecting holes from the injector through the well through the channel through the first insulator onto the charge storage region.
12. An electrically erasable and programmable nonvolatile memory array comprising:
a substrate of semiconductor material of a p-type conductivity;
a well of an n-type conductivity in the substrate; and
a plurality of nonvolatile memory cells arranged in a rectangular array of rows and columns, each of the plurality of nonvolatile memory cells comprising:
an injector having a first region of the p-type conductivity and a second region of the n-type conductivity that is electrically connected to the well; and
a storage transistor comprising a source and a drain formed in the well and having the p-type conductivity, a channel of the well between the source and the drain, a charge storage region disposed over and insulated from the channel by a first insulator, and a control gate disposed over and insulated from the charge storage region by a second insulator.
13. The memory array of claim 12 , wherein for each of the memory cells, the injector is disposed adjacent to and isolated from the channel by an isolation region.
14. The memory array of claim 12 , wherein for each of the memory cells, the charge storage region comprises polysilicon.
15. The memory array of claim 12 , wherein for each of the memory cells, the charge storage region comprises a dielectric having a plurality of spaced-apart nano-crystals of a semiconductor material.
16. The memory array of claim 12 , wherein for each of the memory cells, the charge storage region comprises a dielectric having a plurality of charge storing traps.
17. The memory array of claim 12 , wherein the channel of each of the plurality of nonvolatile memory cells is a first channel, and each of the plurality of nonvolatile memory cells further comprising:
a select transistor having a source and a drain of the p-type conductivity formed in the well with a second channel of the well defined therebetween, and a gate disposed over and insulated from the second channel by a third insulator, wherein the source of the select transistor is electrically connected to the drain of the storage transistor.