Apparatus and method for programming and verifying data in a nonvolatile memory device

An operating method of a memory device, comprising:

• repeatedly performing program loops, comprising a voltage application interval and a verification interval, on cells that have been connected to a word line that have been selected as a program target, among multiple memory cells that have been connected between multiple word lines and multiple bit lines according to an increment step pulse program (ISPP) method until a program operation is completed;
• applying a first program voltage to the selected word line in the voltage application interval of a first program loop, among the program loops that are repeated according to the ISPP method;
• comparing a threshold voltage level of each of cells that have been selected as a verification target, among the cells that have been connected to the selected word line, and a pre-target level lower than a target level in the verification interval of the first program loop after the first application step;
• and
• adjusting an increase in a level of a second program voltage that is applied to the selected word line, based on a result of the comparison step, in the voltage application interval of a second program loop, among the program loops that are repeated according to the ISPP method.