SEMICONDUCTOR MEMORY

PROBLEM TO BE SOLVED: To provide a semiconductor memory including variable resistive elements which can stably and highly controllably perform writing under an intended electric resistance state in a writing operation by a random access.SOLUTION: Despite a resistive state of a variable resistive element of a memory cell to be rewritten (an erasing and writing operation), an erasing voltage pulse for making the resistive state of the variable resistive element a lowest erasure state is applied thereto. Later, a writing voltage pulse for making the resistive state of the variable resistive element an intended writing state is applied to a variable resistive element of the memory cell to be written. The writing voltage pulse is thus applied constantly after the application of the erasing voltage pulse, so as to avoid the continuous application of a plurality of writing voltage pulses. Furthermore, a memory cell array is configured of an even number of sub banks so as to apply the erasing voltage pulse to one sub bank and the writing voltage pulse to another sub bank alternately.