Integrated semiconductor nonvolatile storage device
View Patent ↗An object of the present invention is to provide an integrated semiconductor nonvolatile storage device that can be read at high speed and reprogrammed an increased number of times. In the case of conventional nonvolatile semiconductor storage devices having a split-gate structure, there is a tradeoff between the read current and the maximum allowable number of reprogramming operations. To overcome this problem, an integrated semiconductor nonvolatile storage device of the present invention is configured such that memory cells having different memory gate lengths are integrated on the same chip. This allows the device to be read at high speed and reprogrammed an increased number of times.
1. An integrated semiconductor nonvolatile storage device comprising:
a semiconductor substrate; and
a plurality of semiconductor nonvolatile memory devices formed on said semiconductor substrate, each semiconductor nonvolatile memory device including a first storage portion to store information of a first type and a second storage portion to store information of a second type,
wherein each said first storage portion and each said second storage portion includes a first insulated gate field effect transistor and a second insulated gate field effect transistor having a charge retention portion, and
wherein, for each semiconductor nonvolatile memory device, a channel length of each said second insulated gate field effect transistor of the first storage portion is shorter than a channel length of each said second insulated gate field effect transistor of the second storage portion.
2. An integrated semiconductor nonvolatile storage device as claimed in claim 1 ,
wherein a pair of said first and said second insulated gate field effect transistors include a first gate and a second gate, said first and second gates being disposed in a longitudinal direction parallel to each other, wherein each said first insulated gate field effect transistor includes a first diffusion layer electrode, a second diffusion layer electrode, and a first channel disposed perpendicular to the longitudinal direction of said first and second gates, said first channel being arranged between said first and second diffusion layer electrodes and controlled by said first gate,
wherein each said second insulated gate field effect transistor includes a first diffusion layer electrode, a second diffusion layer electrode, and a second channel, all disposed perpendicular to the longitudinal direction of said first and second gates, said second channel being arranged between said first and second diffusion layer electrodes and controlled by said second gate,
wherein said second insulated gate field effect transistor includes a gate insulating film having a charge retention function, and
wherein said second insulated gate field effect transistor is adapted such that a change in an amount of charge retained in said gate insulating film having said charge retention function results in a change in a relationship between a voltage of said second gate and a current flowing between said first and second diffusion layer electrodes of said second insulated gate field effect transistor.
3. An integrated semiconductor nonvolatile storage device as claimed in claim 2 ,
wherein electrons and holes are injected into said gate insulating film of said second insulated gate field effect transistor such that a change in an amount of carrier charge retained in said gate insulating film results in a change in said relationship between said voltage of said second gate and said current flowing between said first and second diffusion layer electrodes of said second insulated gate field effect transistor.
4. An integrated semiconductor nonvolatile storage device as claimed in claim 2 , wherein said gate insulating film of said second insulated gate field effect transistor is a film stack comprised of a silicon oxide film and a silicon nitride film.
5. An integrated semiconductor nonvolatile storage device as claimed in claim 2 ,
wherein said first insulated gate field effect transistor includes a first insulating film formed on said semiconductor substrate, said first insulating film acting as a gate insulating film and having said first gate thereon,
wherein said second insulated gate field effect transistor includes a second insulating film having a first portion formed on a side of said first gate and a second portion formed on a region of a top surface of said semiconductor substrate, said second portion of said second insulating film having said second gate thereon and acting as a gate insulating film of said second insulated gate field effect transistor.
6. An integrated semiconductor nonvolatile storage device as claimed in claim 5 ,
wherein said second gate is formed on said second insulating film such that both of a side and a bottom of said second gate are in contact with said second insulating film, and
wherein a portion of said second insulating film is arranged between said first gate and said second gate.
7. An integrated semiconductor nonvolatile storage device as claimed in claim 1 , wherein said second insulated gate field effect transistors of the first and second storage portions have the same gate length.
8. An integrated semiconductor nonvolatile storage device as claimed in claim 1 , wherein said plurality of semiconductor nonvolatile memory devices are arranged in at least a first memory mat and a second memory mat such that the semiconductor nonvolatile memory devices of said first memory mat have a shorter channel length than the semiconductor nonvolatile memory devices of said second memory mat.
9. An integrated semiconductor nonvolatile storage device as claimed in claim 8 , wherein said semiconductor nonvolatile memory devices of said first memory mat are read at higher speed than said semiconductor nonvolatile memory devices of said second memory mat.
10. An integrated semiconductor nonvolatile storage device as claimed in claim 8 , wherein said semiconductor nonvolatile memory devices of said second memory mat are reprogrammed a larger number of times than said semiconductor nonvolatile memory devices of said first memory mat.
11. An integrated semiconductor nonvolatile storage device as claimed in claim 1 ,
wherein each said first insulated gate field effect transistor is a select transistor, and
wherein each said second insulated gate field effect transistor is a memory transistor.
12. An integrated semiconductor nonvolatile storage device as claimed in claim 1 ,
wherein the first type of information is code file information, and
wherein the second type of information is data file information.
13. An integrated semiconductor nonvolatile storage device as claimed in claim 1 ,
wherein the first storage portion operates at high speed relative to the second storage portion, and
wherein the second storage portion undergoes a large number of reprogramming operations relative to the first storage portion.
14. An integrated semiconductor nonvolatile storage device comprising:
a semiconductor substrate; and
a plurality of semiconductor nonvolatile memory components formed on said semiconductor substrate, said semiconductor nonvolatile memory components including first memory components each allocated for a first storage portion to store information of a first type and second memory components each allocated for a second storage portion to store information of a second type,
wherein each said semiconductor nonvolatile memory component includes a first insulated gate field effect transistor and a second insulated gate field effect transistor having a charge retention portion, and
wherein a channel length of the second insulated gate field effect transistor of each first memory component is shorter than a channel length of the second insulated gate field effect transistor of each second memory component.
15. An integrated semiconductor nonvolatile storage device as claimed in claim 14 ,
wherein a pair of said first and said second insulated gate field effect transistors include a first gate and a second gate, said first and second gates being disposed in a longitudinal direction parallel to each other,
wherein each said first insulated gate field effect transistor includes a first diffusion layer electrode, a second diffusion layer electrode, and a first channel disposed perpendicular to the longitudinal direction of said first and second gates, said first channel being arranged between said first and second diffusion layer electrodes and controlled by said first gate,
wherein each said second insulated gate field effect transistor includes a first diffusion layer electrode, a second diffusion layer electrode, and a second channel, all disposed perpendicular to the longitudinal direction of said first and second gates, said second channel being arranged between said first and second diffusion layer electrodes and controlled by said second gate,
wherein said second insulated gate field effect transistor includes a gate insulating film having a charge retention function, and
wherein said second insulated gate field effect transistor is adapted such that a change in an amount of charge retained in said gate insulating film having said charge retention function results in a change in a relationship between a voltage of said second gate and a current flowing between said first and second diffusion layer electrodes of said second insulated gate field effect transistor.
16. An integrated semiconductor nonvolatile storage device as claimed in claim 15 ,
wherein electrons and holes are injected into said gate insulating film of said second insulated gate field effect transistor such that a change in an amount of carrier charge retained in said gate insulating film results in a change in said relationship between said voltage of said second gate and said current flowing between said first and second diffusion layer electrodes of said second insulated gate field effect transistor.
17. An integrated semiconductor nonvolatile storage device as claimed in claim 15 , wherein said gate insulating film of said second insulated gate field effect transistor is a film stack comprised of a silicon oxide film and a silicon nitride film.
18. An integrated semiconductor nonvolatile storage device as claimed in claim 15 ,
wherein said first insulated gate field effect transistor includes a first insulating film formed on said semiconductor substrate, said first insulating film acting as a gate insulating film and having said first gate thereon,
wherein said second insulated gate field effect transistor includes a second insulating film having a first portion formed on a side of said first gate and a second portion formed on a region of a top surface of said semiconductor substrate, said second portion of said second insulating film having said second gate thereon and acting as a gate insulating film of said second insulated gate field effect transistor.
19. An integrated semiconductor nonvolatile storage device as claimed in claim 18 ,
wherein said second gate is formed on said second insulating film such that both of a side and a bottom of said second gate are in contact with said second insulating film, and
wherein a portion of said second insulating film is arranged between said first gate and said second gate.
20. An integrated semiconductor nonvolatile storage device as claimed in claim 14 , wherein said second insulated gate field effect transistors of the first and second storage portions have the same gate length.
21. An integrated semiconductor nonvolatile storage device as claimed in claim 14 ,
wherein each said first insulated gate field effect transistor is a select transistor, and
wherein each said second insulated gate field effect transistor is a memory transistor.
22. An integrated semiconductor nonvolatile storage device as claimed in claim 14 ,
wherein the first type of information is code file information, and
wherein the second type of information is data file information.
23. An integrated semiconductor nonvolatile storage device as claimed in claim 14 ,
wherein the first storage portion operates at high speed relative to the second storage portion, and
wherein the second storage portion undergoes a large number of reprogramming operations relative to the first storage portion.