Non-volatile semiconductor memory device in which program disturb is reduced and method of programming the same
A non-volatile semiconductor memory device capable of reducing program disturb and a method of programming the same are provided. A bit line connected to a non-selected memory cell in the same block as a selected memory cell enters a floating state by inactivating a bit line selection switch, so that voltage levels of an first conductivity type channel and a source/drain terminal formed in a pocket second conductivity type well below a memory transistor have an intermediate level of a voltage level of a selection line and the pocket P type well. Therefore, program disturb caused by FN tunneling and junction hot electrons can be inhibited.
1. A non-volatile semiconductor memory device, comprising:
at least one memory cell block including a plurality of memory cells, each memory cell including a memory transistor and a selection transistor serially connected between a plurality of bit lines and a common source line, the memory transistor and the selection transistor having gates respectively connected to a plurality of selection lines and a plurality of word lines disposed in a direction perpendicular to the bit lines;
a bit line selection switch block including a plurality of bit line selection switches configured to electrically connect the bit lines with corresponding global bit lines in response to voltages applied to a plurality of bit line selection switch lines, respectively; and
a controller configured to decode an address applied externally at the time of a program operation, control the voltage applied to the bit line selection switch line, and electrically disconnect a bit line that is not selected from the global bit line to float the bit line that is not selected.
2. The non-volatile semiconductor memory device as claimed in claim 1 , further comprising:
a first conductive type substrate;
a second conductive type deep well formed in a predetermined area within the substrate; and
a first conductive type pocket well formed in a predetermined area within the deep well,
wherein the memory cell block and the bit line selection switch block are formed in the pocket well.
3. The non-volatile semiconductor memory device as claimed in claim 2 , wherein, at the time of the program operation, when the decoded address selects the memory cell block, the controller is configured to:
apply a first negative voltage to the word lines and a second negative voltage to the pocket well;
float the common source line;
decode a row address of the address; and
apply a first positive voltage to the selection line which is selected and a ground voltage to the selection line which is not selected.
4. The non-volatile semiconductor memory device as claimed in claim 3 , wherein when data applied from the outside is 1, a third negative voltage is applied to the global bit line.
5. The non-volatile semiconductor memory device as claimed in claim 4 , wherein, at the time of the program operation, the controller is configured to:
decode a column address of the address;
apply a second positive voltage to a bit line selection switch line that is selected; and
apply a fourth negative voltage to a bit line selection switch line that is not selected.
6. The non-volatile semiconductor memory device as claimed in claim 5 , wherein the first positive voltage has a voltage level with a larger absolute value than the first to fourth negative voltages, the second positive voltage has a voltage level with a smaller absolute value than the first to third negative voltages, and the fourth negative voltage has a voltage level with a smaller absolute value than the second positive voltage.
7. A method of programming a non-volatile semiconductor memory device which includes at least one memory cell block including a plurality of memory cells, each memory cell including a memory transistor and a selection transistor serially connected between a plurality of bit lines and a common source line, the memory transistor and the selection transistor having gates respectively connected to a plurality of selection lines and a plurality of word lines disposed in a direction perpendicular to the bit lines, and a bit line selection switch block, including a plurality of bit line selection switches configured to electrically connect the bit lines with corresponding global bit lines in response to voltages applied to a plurality of bit line selection switch lines, respectively, the method comprising, at the time of a program operation:
decoding an address applied externally;
controlling the voltage applied to the bit line selection switch line; and
electrically disconnecting a bit line that is not selected from the global bit line to float the bit line that is not selected.
8. The method as claimed in claim 7 , further comprising, at the time of the program operation, when the decoded address selects the memory cell block:
applying a first negative voltage to the word lines;
applying a second negative voltage to a pocket well in which the memory cell block and the bit line selection switch block are formed; and
floating the common source line.
9. The method as claimed in claim 8 , further comprising, at the time of the program operation:
decoding a row address of the address;
applying a first positive voltage having a voltage level having a larger absolute value than the first and second negative voltages to the selection line which is selected and a ground voltage to the selection line which is not selected; and
when data applied from the outside is 1, applying a third negative voltage having a voltage level having a smaller absolute value than the first positive voltage to the corresponding global bit line.
10. The method as claimed in claim 9 , wherein floating the bit line comprises
decoding a column address of the address; and
applying a second positive voltage, having a voltage level having a smaller absolute value than the first to third negative voltages, to a bit line selection switch line that is selected and a fourth negative voltage, having a voltage level which is smaller in absolute value than the second positive voltage, to a bit line selection switch line that is not selected.