Semiconductor device
View Patent ↗A semiconductor device including a nonvolatile memory unit and a variable logic unit mounted on a chip is configured to achieve higher speed operation at a lower voltage. The semiconductor device includes a nonvolatile memory unit comprising a plurality of rewritable nonvolatile memory cells and a variable logic unit whose logical functions are determined, according to logic constitution definition data to be loaded into storage cells thereof. A nonvolatile memory cell essentially has a split gate structure composed of a selecting MOS transistor and a memory MOS transistor and constructed such that the dielectric withstand voltage of the gate of the selecting MOS transistor is lower than that of the memory MOS transistor or the gate insulation layer of the selecting MOS transistor is thinner than that of a high-voltage-tolerant MOS transistor. Because the selecting MOS transistor has a high Gm, a sufficiently great current for reading can be obtained.
1. A semiconductor device comprising:
a nonvolatile memory unit including a plurality of rewritable nonvolatile memory cells;
a variable logic unit including a plurality of storage cells; and
a write permission circuit,
wherein logical functions of the variable logic unit are determined in accordance with logic constitution definition data to be loaded into the plurality of storage cells,
wherein each of said nonvolatile memory cells has a first MOS transistor for storing data and a second MOS transistor for selecting the first transistor,
wherein a first gate electrode of the first MOS transistor and a second gate electrode of the second MOS transistor are provided over a first region between a first impurity region and a second impurity region,
wherein the first region has no common impurity region for the first and second MOS transistor,
wherein a gate breaks down immunity voltage of the second MOS transistor is lower than a gate breaks down immunity voltage of the first MOS transistor, and
wherein the write permission circuit limits to write the logic constitution definition data from outside of the semiconductor device.
2. A semiconductor device according to claim 1 , further comprising:
an IO circuit,
wherein when a password is inputted to the semiconductor device via the IO circuit, the write permission circuit permits to write the logic constitution definition data from outside of the semiconductor device.
3. A semiconductor device according to claim 1 , further comprising:
a terminal,
wherein when a predetermined signal is supplied to the terminal, the write permission circuit permits to write the logic constitution definition data from outside of the semiconductor device.
4. A semiconductor device according to claim 1 ,
wherein the nonvolatile memory unit has a first storage area and a second storage area,
wherein when a password is inputted, the write permission circuit permits to write data into the first storage area, and
wherein the second storage area is permitted to write data without the password.
5. A semiconductor device according to claim 1 ,
wherein the first MOS transistor includes a conductive floating gate electrode covered with an insulation layer under the first gate electrode as a charge-storing region.
6. A semiconductor device according to claim 1 ,
wherein the first MOS transistor includes a charge-trapping insulation layer covered with an insulation layer under the first gate electrode as a charge-storing region.
7. A semiconductor device according to claim 1 , further comprising:
a CPU coupled to the nonvolatile memory unit and the variable logic unit,
wherein the logic constitution definition data is stored in the nonvolatile memory unit.
8. A semiconductor device according to claim 7 ,
wherein the nonvolatile memory unit stores a control program performed by the CPU, and
wherein the CPU uses logical function of the variable logic unit set according to the logic constitution definition data by performing the control program.
9. A semiconductor device comprising:
a nonvolatile memory unit including a plurality of rewritable nonvolatile memory cells, a memory access circuit, and voltage circuit;
a variable logic unit including a plurality of storage cells; and
a write permission circuit,
wherein logical functions of the variable logic unit are determined in accordance with logic constitution definition data to be loaded into the plurality of storage cells,
wherein each of the plurality of rewritable nonvolatile memory cells has a first MOS transistor for storing data and a second MOS transistor for selecting the first MOS transistor,
wherein the memory access circuit has a third MOS transistor and performs logic operation for memory action to the nonvolatile memory cell,
wherein the voltage circuit has a fourth MOS transistor and supplies a voltage for rewriting the data to said nonvolatile memory cell,
wherein a first gate electrode of the first MOS transistor and a second gate electrode of the second MOS transistor are provided over a first region between a first impurity region and a second impurity region,
wherein the first region has no common impurity region for the first and second MOS transistor,
wherein gate insulation layers of the second, third, and fourth MOS transistors are formed to have their physical thicknesses fulfilling constraint tL<=ts<tH where ts is the physical thickness of the gate insulation layer of the second MOS transistor, tL is the physical thickness of the gate insulation layer of the third MOS transistor, and tH is the physical thickness of the gate insulation layer of the fourth MOS transistor, and
wherein the write permission circuit limits to write the logic constitution definition data from outside of the semiconductor device.
10. A semiconductor device according to claim 9 , further comprising:
an IO circuit,
wherein when a password is inputted to the semiconductor device via the IO circuit, the write permission circuit permits to write the logic constitution definition data from outside of the semiconductor device.
11. A semiconductor device according to claim 9 , further comprising:
a terminal,
wherein when a predetermined signal is supplied to the terminal, the write permission circuit permits to write the logic constitution definition data from outside of the semiconductor device.
12. A semiconductor device according to claim 9 ,
wherein the nonvolatile memory unit has a first storage area, and a second storage area,
wherein when a password is inputted, the write permission circuit permits to write data into the first storage area, and
wherein the second storage area is permitted to write data without the password.
13. A semiconductor device according to claim 9 ,
wherein the first MOS transistor includes a conductive floating gate electrode covered with an insulation layer under the first gate electrode as a charge-storing region.
14. A semiconductor device according to claim 9 ,
wherein the first MOS transistor includes a charge-trapping insulation layer covered with an insulation layer under the first gate electrode as a charge-storing region.
15. A semiconductor device according to claim 9 , further comprising:
a CPU coupled to the nonvolatile memory unit and the variable logic unit,
wherein the logic constitution definition data is stored in the nonvolatile memory unit.
16. A semiconductor device according to claim 15 ,
wherein the nonvolatile memory unit stores a control program performed by the CPU, and
wherein the CPU uses logical function of the variable logic unit set according to the logic constitution definition data by performing the control program.