Operating method of non-volatile memory device

PURPOSE: A method for operating a nonvolatile memory device is provided to improve an operation property of a memory device by reducing the width of a threshold voltage distribution in a memory cell with an erase state. CONSTITUTION: A cell block with a plurality of memory cells is erased. A word line of a string including the memory cell is grouped into two or more groups. A first soft program operation is performed in all memory cells of the string(S521). The first soft program operation is verified based on a preset verification voltage(S522). A second soft program operation is performed in the memory cell connected to the word line of each group(S531). A second soft program operation is verified based on the preset verification voltage(S532). [Reference numerals] (AA) Start; (B1,B2,B3,B4,B5,B6) Failure; (C1,C2,C3,C4,C5,C6) Success; (DD) End; (S510) Inputting an erase command; (S511) Applying an erase voltage; (S512) Verifying an erase; (S521) Applying a soft program voltage(WL0~WL63); (S522) Verifying a soft program(WL0~WL63); (S531) Applying a soft program voltage(WL0~WL15); (S532) Verifying a soft program(WL0~WL15); (S541) Applying a soft program voltage(WL16~WL31); (S542) Verifying a soft program(WL16~WL31); (S551) Applying a soft program voltage(WL32~WL47); (S552) Verifying a soft program(WL32~WL47); (S561) Applying a soft program voltage(WL48~WL63); (S562) Verifying a soft program(WL48~WL63)