In a method of writing data in a memory device, a plurality of duplicated bit rows is generated by performing a first duplication operation in which a plurality of bits included in write data are copied by units of bits. A plurality of duplicated bit groups is generated by performing a second duplication operation in which the plurality of duplicated bit rows is copied by units of rows. The plurality of duplicated bit groups is stored into a plurality of memory regions included in the memory device, respectively. Each of the plurality of memory regions is a region that is simultaneously sensed during a data read operation.