US Patent 11935576 Semiconductor device performing row hammer refresh operation

An apparatus includes a memory cell array including a plurality of word lines each coupled to a plurality of memory cells, and a control circuit which is configured to activate first and second internal signals in a time-division manner in response to a first external command A first number of the word lines arc selected in response to the first internal signal, and a second number of the word line is selected in response to the second internal signal. The second number is smaller than the first number.