A non-volatile memory device includes a memory cell array including a memory cell array having word lines, bit lines, and non-volatile memory cells, each non-volatile memory cell having a variable resistive material and an access element connected between the corresponding word line and the corresponding bit line. The variable resistive material has a resistance level that varies according to data to be stored. A selection circuit selects at least one non-volatile memory cell in which data will be written. An adaptive write circuit/method supplies a write bias to the selected non-volatile memory cell through the bit line connected to the selected non-volatile memory cell to write data in the selected non-volatile memory cell and varies (e.g., increases) the write bias until the resistance level of the selected non-volatile memory cell varies.