Abstract: In a non-volatile memory system, a plurality of main memory cells for storing data is arranged in a data cell array and a plurality of reference memory cells is arranged in a reference cell array. The reference cell array includes first reference word lines connected to first reference memory cells and extending, second reference word lines connected to second reference memory cells and extending alternately with the first reference word lines, reference bit lines to which the first and the second reference memory cells are alternately connected in a line and a combined cell having a pair of the first and second reference memory cells and generating a reference signal for processing the data. The first and the second reference memory cells have different cell characteristics. The stability of the reference signal is improved irrespective of the differentiation of the first and the second reference memory cells.

Abstract: In a method of storing data in a nonvolatile memory device, a program operation is performed on target memory cells among a plurality of memory cells based on a program voltage. A verification operation is performed on the target memory cells based on a verification voltage to determine whether all of the target memory cells are completely programmed. The verification voltage is changed depending on the program operation.

Abstract: In a non-volatile memory system, a plurality of main memory cells for storing data is arranged in a data cell array and a plurality of reference memory cells is arranged in a reference cell array. The reference cell array includes first reference word lines connected to first reference memory cells and extending, second reference word lines connected to second reference memory cells and extending alternately with the first reference word lines, reference bit lines to which the first and the second reference memory cells are alternately connected in a line and a combined cell having a pair of the first and second reference memory cells and generating a reference signal for processing the data. The first and the second reference memory cells have different cell characteristics. The stability of the reference signal is improved irrespective of the differentiation of the first and the second reference memory cells.

Abstract: In a method of storing data in a nonvolatile memory device, a program operation is performed on target memory cells among a plurality of memory cells based on a program voltage. A verification operation is performed on the target memory cells based on a verification voltage to determine whether all of the target memory cells are completely programmed. The verification voltage is changed depending on the program operation.