Semiconductor device
Provided is a semiconductor device including nonvolatile memory cells each including a FinFET having excellent memory characteristics. The semiconductor device includes a semiconductor substrate, memory cells each formed in the semiconductor substrate and having a split-gate structure including an opposed-gate selection gate electrode, a memory gate electrode, and a pair of terminals, and a word line driver circuit which supplies a selection voltage to a selection gate electrode of the selected one of the memory cells and supplies a non-selection voltage to the selection gate electrode of the non-selected one of the memory cells. The word line driver circuit supplies, as the non-selection voltage, a voltage which is negative or positive relative to a potential in the semiconductor substrate so as to bring a selection transistor corresponding to the selection gate electrode of the non-selected memory cell into an OFF state.
1. A semiconductor device, comprising:
a first semiconductor region;
a plurality of memory cells, each formed in the first semiconductor region and having a split-gate structure including an opposed-gate selection gate electrode, a memory gate electrode, and a pair of terminals; and
a first driver circuit which supplies a selection voltage to the selection gate electrode of a selected one of the memory cells and supplies a non-selection voltage to the selection gate electrode of a non-selected one of the memory cells,
wherein the first driver circuit supplies, as the non-selection voltage, a voltage which is negative or positive relative to a potential in the first semiconductor region so as to bring a selection transistor corresponding to the selection gate electrode of the non-selected memory cell into an OFF state, and further comprising:
a threshold voltage determination circuit which determines a threshold voltage of the selection transistor corresponding to the selection gate electrode of each of the memory cells,
wherein the first driver circuit supplies, as the non-selection voltage, a voltage based on the threshold voltage determined by the threshold voltage determination circuit to the selection gate electrode of the non-selected memory cell.
2. The semiconductor device according to claim 1 ,
wherein the memory cells are arranged in the form of a matrix in the first semiconductor region,
wherein one of the pair of terminals of each of the memory cells disposed in a row of the matrix is coupled to a bit line disposed in the same row and the selection gate electrode of each of the memory cells disposed in a column of the matrix is coupled to a word line disposed in the same column, while the memory gate electrode of each of the memory cells disposed in the column is coupled to a memory gate line disposed in the same column and the other of the pair of terminals of each of the memory cells disposed in the column is coupled to a source line, and
wherein the first driver circuit supplies the non-selection voltage to the selection gate electrode of the non-selected memory cell via the word line.
3. The semiconductor device according to claim 2 ,
wherein the semiconductor device includes a second semiconductor region electrically isolated from the first semiconductor region, and
wherein the first driver circuit is disposed in the second semiconductor region.
4. The semiconductor device according to claim 2 ,
wherein the threshold voltage determination circuit includes:
a determination memory cell having a split-gate structure including an opposed-gate selection gate electrode, a memory gate electrode, and a pair of terminals; and
a determination circuit which determines the threshold voltage of the selection transistor on the basis of a current flowing in the determination memory cell and a voltage in the selection gate electrode.
5. The semiconductor device according to claim 4 ,
wherein each of a plurality of ones of the memory cells arranged in the form of the matrix is used as the determination memory cell.
6. The semiconductor device according to claim 2 ,
wherein the selection transistor corresponding to the selection gate electrode of each of the memory cells is an N-channel transistor, and
wherein the non-selection voltage is negative relative to the potential in the first semiconductor region.
7. The semiconductor device according to claim 2 ,
wherein the selection transistor corresponding to the selection gate electrode of each of the memory cells is a P-channel transistor, and
wherein the non-selection voltage is positive relative to the potential in the first semiconductor region.
8. The semiconductor device according to claim 2 ,
wherein the respective memory gate electrodes of the memory cells include an opposed-gate memory gate electrode.
9. The semiconductor device according to claim 8 ,
wherein the memory cells include an electrically rewritable nonvolatile memory cell having a split-gate structure using a FinFET.
10. A semiconductor device, comprising:
a plurality of memory cells arranged in the form of a matrix and each having a split-gate structure including an opposed-gate selection gate electrode, a memory gate electrode, and a pair of semiconductor regions functioning as a source region and a drain region;
a plurality of bit lines disposed in individual rows of the matrix on a one-to-one basis and each coupled to one of the pair of semiconductor regions of each of the memory cells disposed in the same row;
a plurality of word lines disposed in individual columns of the matrix on a one-to-one basis and each coupled to the selection gate electrode of each of the memory cells disposed in the same column;
a source line coupled to the other of the pair of semiconductor regions of each of the memory cells disposed in the same column of the matrix; and
a word line driver circuit coupled to the word lines to supply a selection voltage to a selected one of the word lines and supplies a non-selection voltage to a non-selected one of the word lines,
wherein the word line driver circuit supplies, as the non-selection voltage, a voltage which is negative or positive relative to a voltage in either one of the pair of semiconductor regions of each of the memory cells coupled to the non-selected word line so as to bring a selection transistor corresponding to the selection gate electrode of each of the memory cells coupled to the non-selected word line into an OFF state, and further comprising:
a threshold voltage determination circuit which determines a threshold voltage of the selection transistor,
wherein the word line driver circuit supplies, as the non-selection voltage, a voltage based on the threshold voltage determined by the threshold voltage determination circuit to the word line.
11. The semiconductor device according to claim 10 ,
wherein the memory cells are formed in a first semiconductor region, while the word line driver circuit is formed in a second semiconductor region electrically isolated from the first semiconductor region.
12. The semiconductor device according to claim 11 ,
wherein the threshold voltage determination circuit uses each of a plurality of ones of the memory cells arranged in the form of the matrix as a determination memory cell to determine the threshold voltage of the selection transistor corresponding to the selection gate electrode on the basis of a voltage in the selection gate electrode of the determination memory cell and a current flowing in the determination memory cell.
13. The semiconductor device according to claim 11 ,
wherein the memory gate electrodes include an opposed-gate memory gate electrode.