Semiconductor memory device and method of operating the same

A semiconductor memory device, comprising:

• a memory cell array including a plurality of memory cells;
• a peripheral circuit configured to perform a program operation of programming data in memory cells coupled to a selected word line, among the plurality of memory cells;
• and
• a control logic configured to control the peripheral circuit such that, during the program operation, a first program loop for storing first page data and a second program loop for storing second page data according to a foggy-fine programming scheme,
• wherein the control logic is configured to control the peripheral circuit such that, during execution of the second program loop, flag data is programmed in a flag cell, among memory cells coupled to the selected word line, after a foggy programming of the second page data is completed.

A method of operating a semiconductor memory device, comprising:

• programming selected memory cells with first page data;
• and
• performing a program operation of flag data and second page data on the basis of an operation of verifying at least one program state, among a plurality of program states, wherein the plurality of program states include a first program state to a (2N−1)-th program state, where N is a natural number of 2 or more,
• wherein the flag data indicates whether data programmed according to the program operation is the first page data or the second page data, and
• wherein during the program operation of the second page data and the flag data, the program operation of the flag data is initiated after an operation of verifying at least one of the first program state and the (2N−1)-th program state.