Non-volatile two-transistor programmable logic cell and array layout
View Patent ↗A two-transistor non-volatile memory cell is formed in a semiconductor body. A memory-transistor well is disposed within the semiconductor body. A switch-transistor well is disposed within the semiconductor body and is electrically isolated from the memory transistor well. A memory transistor including spaced-apart source and drain regions is formed within the memory-transistor well. A switch transistor including spaced-apart source and drain regions is formed within the switch-transistor well region. A floating gate is insulated from and self aligned with the source and drain regions of the memory transistor and switch transistor. A control gate is disposed above and aligned to the floating gate and with the source and drain regions of the memory transistor and the switch transistor.
1. A non-volatile memory cell including:
a semiconductor body;
a memory-transistor well disposed within the semiconductor body;
a first switch-transistor well disposed within the semiconductor body to a first side of the memory transistor well and electrically isolated from the memory transistor well;
a second switch-transistor well disposed within the semiconductor body to a second side of the memory transistor well opposite the first side and electrically isolated from the memory transistor well;
a memory transistor formed within the memory-transistor well and including spaced-apart source and drain regions;
a first switch transistor formed within the first switch-transistor well region and including spaced-apart source and drain regions;
a second switch transistor formed within the second switch-transistor well region and including spaced-apart source and drain regions;
a floating gate insulated from and self aligned with the source and drain regions of the memory transistor and the first and second switch transistors; and
a control gate disposed above and self aligned with respect to the floating gate and with the source and drain regions of the memory transistor and the first and second switch transistor.
2. The non-volatile memory cell of claim 1 , further including:
at least one additional switch transistor disposed in the first switch-transistor well and sharing a floating gate and a control gate with the memory transistor; and
at least one additional switch transistor disposed in the second switch-transistor well and sharing a floating gate and a control gate with the memory transistor.
3. The non-volatile memory cell of claim 1 wherein:
the semiconductor body is n-type;
the memory-transistor well and the switch transistor wells are all p-type wells; and
the memory transistor and the switch transistors are all n-channel transistors.
4. The non-volatile memory cell of claim 3 wherein the semiconductor body is an n-type well disposed in a p-type semiconductor substrate.
5. The non-volatile memory cell of claim 4 , further including:
an enhanced memory-transistor p-type well region disposed about the periphery of the memory-transistor p-type well; and
an enhanced switch-transistor p-type well region disposed about the periphery of the switch-transistor p-type wells.
6. The non-volatile memory cell of claim 3 wherein:
the semiconductor body is an n-type well formed in a semiconductor substrate; and
the switch-transistor p-type wells are spaced apart from the memory-transistor p-type well and are isolated from the memory transistor p-type well by the n-type well.
7. The non-volatile memory cell of claim 6 , further including:
at least one additional switch transistor disposed in the first switch-transistor well and sharing a floating gate and a control gate with the memory transistor; and
at least one additional switch transistor disposed in the second switch-transistor well and sharing a floating gate and a control gate with the memory transistor.
8. The non-volatile memory cell of claim 3 wherein:
the semiconductor body is a n-type well formed in a semiconductor substrate; and
the switch-transistor p-type wells are spaced apart from the memory-transistor p-type well and are isolated from the memory-transistor p-type well by the n-type well and by a second n-type well formed in the n-type well between the switch-transistor p-type wells and the memory-transistor p-type well.
9. The non-volatile memory cell of claim 8 , further including:
at least one additional switch transistor disposed in the first switch-transistor well and sharing a floating gate and a control gate with the memory transistor; and
at least one additional switch transistor disposed in the second switch-transistor well and sharing a floating gate and a control gate with the memory transistor.
10. The non-volatile memory cell of claim 8 , wherein edges of the second n-type well are spaced apart from edges of the memory-transistor p-type well and the switch-transistor p-type well.
11. The non-volatile memory cell of claim 10 , further including a deep n-type well disposed below the second n-type well.
12. The non-volatile memory cell of claim 11 , wherein edges of the second n-type well and the deep n-type well are spaced apart from edges of the memory-transistor p-type well and the switch-transistor p-type wells.
13. The non-volatile memory cell of claim 3 , wherein the memory-transistor wells are optimized for memory-transistor characteristics and the switch-transistor wells are optimized for switch-transistor characteristics.
14. The non-volatile memory cell of claim 3 , wherein the memory-transistor well and the switch-transistor wells are formed to different depths.
15. The non-volatile memory cell of claim 1 , wherein the memory-transistor well is electrically isolated from the switch-transistor wells by a deep-trench isolation region.