Granted Patent B2

US 7,262,995 · App. 11/379,455 · Granted Aug 28, 2007

Abstract

Claims (10)

1. A method for reading an NAND-type flash memory apparatus having a plurality of cell strings, each of which a plurality of cells is serially connected to, a plurality of bit lines, each of which is connected to a common drain terminal of the corresponding cell string to select the cell strings, a common source line connected to a common source terminal of the cell strings, a plurality of word lines intersecting the bit lines to select the respective cells, comprising the steps of:

selecting a cell to read a state thereof by selecting the corresponding bit line and the corresponding word line;

applying a ground voltage to the selected word line, applying a pass voltage to the other non-selected word lines, applying a power supply voltage to the other non-selected bit lines, applying a read voltage to the selected bit line, and applying the power supply voltage to the common source line, wherein the read voltage is lower than the power supply voltage and higher than the ground voltage; and

reading information stored in the selected cell by comparing a voltage of the selected bit line with a reference voltage.

2. The method for reading an NAND-type flash memory apparatus according to claim 1 , wherein the selected cell is read as a programmed state when the read voltage applied to the selected bit line is equal to or lower than the reference voltage, and wherein the selected cell is read as an erased state when the read voltage applied to the selected bit line is higher than the reference voltage.

3. The method of reading a NAND-type flash memory apparatus according to claim 1 , wherein the read voltage is used as the reference voltage.

4. The method for reading a NAND-type flash memory apparatus according to claim 1 , wherein a voltage of 1V or a half of the power supply voltage is used as the read voltage.

5. The method for reading a NAND-type flash memory apparatus according to claim 1 , wherein a voltage of 3V to 5V which is higher than a threshold voltage of the programmed cell is used as the pass voltage.

6. The method for reading a NAND-type flash memory apparatus according to claim 1 , wherein, when the selected cell is in an erased state, the read voltage applied to the selected bit line is increased by a product of a current flowing the selected cell and a determination time divided by a line capacitance.

7. The method for reading a NAND-type flash memory apparatus according to claim 1 , wherein, when the selected cell is in a programmed state, the read voltage applied to the selected bit line is increased by a product of a leakage current flowing the cell connected to the selected bit line and a determination time divided by a line capacitance.

Assignments (8)