Semiconductor storage device

1. A semiconductor storage device comprising:

a plurality of memory cell transistors above a semiconductor substrate, including first, second, third, and fourth memory cell transistors, wherein the first and second memory cell transistors are at opposite sides of a first semiconductor body in which channel regions of the first and second memory cell transistors are located, and third and fourth memory cell transistors are at opposite sides of a second semiconductor body in which channel regions of the third and fourth memory cell transistors are located;

first, second, third, and fourth select transistors connected to the first, second, third, and fourth memory cell transistors, respectively;

a plurality of word lines including a first word line connected to gates of the first and third memory cell transistors, and a second word line connected to gates of the second and fourth memory cell transistors;

a first bit line connected to the first and second select transistors;

a second bit line connected to the third and fourth select transistors; and

a controller configured to perform a write operation on the first to fourth memory cell transistors in a plurality of loops, each loop including a program operation and a verify operation, wherein

during a program operation on the third memory cell transistor, the controller determines a program voltage to be applied to the first word line on the basis of a first number of loops, which is determined during the write operation performed on the first memory cell transistor, and

during a program operation on the fourth memory cell transistor, the controller determines a program voltage to be applied to the second word line on the basis of a second number of loops, which is determined during the write operation performed on the second memory cell transistor.

2. The semiconductor storage device according to claim 1 , wherein

the program voltage that the controller determines during the program operation on the third memory cell transistor is an initial program voltage to be applied to the first word line during the write operation performed on the third memory cell transistor, and

the program voltage that the controller determines during the program operation on the fourth memory cell transistor is an initial program voltage to be applied to the second word line during the write operation performed on the fourth memory cell transistor.

3. The semiconductor storage device according to claim 2 , wherein

the initial program voltage to be applied to the first word line during the write operation performed on the third memory cell transistor is greater than an initial program voltage applied to the first word line during the write operation performed on the first memory cell transistor, and

the initial program voltage to be applied to the second word line during the write operation performed on the fourth memory cell transistor is greater than an initial program voltage applied to the second word line during the write operation performed on the second memory cell transistor.

4. The semiconductor storage device according to claim 2 , wherein

during the program operation on the third memory cell transistor, the controller determines the initial program voltage to be applied to the first word line on the basis of the first number of loops minus one, and

during the program operation on the fourth memory cell transistor, the controller determines the initial program voltage to be applied to the second word line on the basis of the second number of loops minus one.

5. The semiconductor storage device according to claim 1 , wherein:

the plurality of memory cell transistors further includes a fifth memory cell transistor connected between the first memory cell transistor and the first select transistor, a sixth memory cell transistor connected between the second memory cell transistor and the second select transistor, a seventh memory cell transistor connected between the third memory cell transistor and the third select transistor, and an eighth memory cell transistor connected between the fourth memory cell transistor and the fourth select transistor;

the plurality of word lines further includes a third word line connected to gates of the fifth and seventh memory cell transistors, and a fourth word line connected to gates of the sixth and eighth memory cell transistors; and

the controller stores a difference between the first and second number of loops, and during a program operation on the sixth and eighth memory cell transistors, the controller determines a program voltage to be applied to the fourth word line on the basis of the stored difference.

6. The semiconductor storage device according to claim 1 , wherein

the first number of loops is determined on the basis of a minimum number of loops that were executed during the write operation performed on the first memory cell transistor for a threshold voltage of the first memory cell transistor to be raised to at least a first voltage, and

the second number of loops is determined on the basis of a minimum number of loops that were executed during the write operation performed on the second memory cell transistor for a threshold voltage of the second memory cell transistor to be raised to at least a second voltage.

7. The semiconductor storage device according to claim 1 , wherein

during the verify operations, a number of verification voltages are applied, and

the first and second voltages are less than a lowest one of the verification voltages.

8. The semiconductor storage device according to claim 1 , wherein

during the verify operations, a number of verification voltages are applied, and

the first and second voltages are equal to a lowest one of the verification voltages.

9. The semiconductor storage device according to claim 1 , wherein the write operations on the first and third memory cell transistors are performed sequentially, and the write operations on the second and fourth memory cell transistors are performed sequentially.

10. The semiconductor storage device according to claim 1 , wherein the write operations on the first, second, third, and fourth memory cell transistors are performed sequentially.

11. The semiconductor storage device according to claim 1 , wherein first and second semiconductor bodies are each a semiconductor pillar that extends above the semiconductor substrate.

12. The semiconductor storage device according to claim 11 , wherein

the channel regions for the first and second memory cell transistors are located in the first semiconductor body and are electrically connected, and

the channel regions for the third and fourth memory cell transistors are located in the second semiconductor body and are electrically connected.

13. The semiconductor storage device according to claim 11 , wherein

the channel regions for the first and second memory cell transistors are located in the first semiconductor body and are electrically isolated, and

the channel regions for the third and fourth memory cell transistors are located in the second semiconductor body and are electrically isolated.

14. The semiconductor storage device according to claim 1 , further comprising:

first and second insulating pillars extending above the semiconductor substrate, wherein the first semiconductor body is between the first and second insulating pillars, and

third and fourth insulating pillars extending above the semiconductor substrate, wherein the second semiconductor body is between the first and second insulating pillars.

15. A semiconductor storage device comprising:

a plurality of memory cell transistors above a semiconductor substrate, including first, second, third, and fourth groups of memory cell transistors, wherein the first and second groups of memory cell transistors are respectively at opposite sides of a first group of semiconductor pillars spaced apart and aligned along a first direction, and the third and fourth groups of memory cell transistors are respectively at opposite sides of a second group of semiconductor pillars spaced apart and aligned along the first direction, and the first group of semiconductor pillars is spaced apart from the second group of semiconductor pillars in a second direction crossing the first direction;

a plurality of word lines stacked above the semiconductor substrate, including first and second word lines at a same level above the semiconductor substrate, wherein the first word line is connected to gates of the memory cell transistors in the first and third groups of memory cell transistors and the second word line is connected to gates of the memory cell transistors in the second and fourth groups of memory cell transistors; and

a controller configured to perform a write operation per group of memory cell transistors connected to one word line, wherein

during a write operation performed on the third group of memory cell transistors connected to the first word line, the controller determines an initial program voltage to be applied to the first word line on the basis of a first number of loops, which is determined during the write operation performed on the first group of memory cell transistors connected to the first word line, and

during a write operation performed on the fourth group of memory cell transistors connected to the second word line, the controller determines an initial program voltage to be applied to the second word line on the basis of a second number of loops, which is determined during the write operation performed on the second group of memory cell transistors connected to the second word line.

16. The semiconductor storage device according to claim 15 , wherein the write operations on the first and third groups of memory cell transistors are performed sequentially, and the write operations on the second and fourth groups of memory cell transistors are performed sequentially.

17. The semiconductor storage device according to claim 15 , wherein the write operations on the first, second, third, and fourth groups of memory cell transistors are performed sequentially.

18. A method of performing a write operation on a semiconductor storage device comprising a plurality of memory cell transistors above a semiconductor substrate, including first, second, third, and fourth memory cell transistors, wherein the first and second memory cell transistors are at opposite sides of a first semiconductor body in which channel regions of the first and second memory cell transistors are located, and third and fourth memory cell transistors are at opposite sides of a second semiconductor body in which channel regions of the third and fourth memory cell transistors are located, and a plurality of word lines including a first word line connected to gates of the first and third memory cell transistors, and a second word line connected to gates of the second and fourth memory cell transistors, said method comprising:

executing a write operation on the first memory cell transistor and then executing a write operation on the third memory cell transistor; and

executing a write operation on the second memory cell transistor and then executing a write operation on the fourth memory cell transistor, wherein

during the write operation performed on the third memory cell transistor, an initial program voltage applied to the first word line is set on the basis of a first number of loops, which is determined during the write operation performed on the first memory cell transistor, and

during the program operation performed on the fourth memory cell transistor, an initial program voltage applied to the second word line is set on the basis of a second number of loops, which is determined during the write operation performed on the second memory cell transistor.

19. The method of claim 18 , further comprising:

during the write operation performed on the first memory cell transistor, counting a first minimum number of loops, which is the number of loops required for a threshold voltage of the first memory cell transistor to reach a first voltage, and storing the first minimum number of loops as the first number of loops, and

during the write operation performed on the second memory cell transistor, counting a second minimum number of loops, which is the number of loops required for a threshold voltage of the second memory cell transistor to reach a second voltage, and storing the second minimum number of loops as the second number of loops.

20. The method of claim 19 , wherein

the initial program voltage applied to the first word line during the write operation performed on the third memory cell transistor is greater than an initial program voltage applied to the first word line during the write operation performed on the first memory cell transistor, and

the initial program voltage applied to the second word line during the write operation performed on the fourth memory cell transistor is greater than an initial program voltage applied to the second word line during the write operation performed on the second memory cell transistor.