The effect of the crystal grown-in defects on the pause tail characteristics of megabit dynamic random access memory devices was investigated. By comparing the performance of the devices fabricated on epitaxial silicon wafers with those fabricated on polished Czochralski silicon wafers, it was found that the refresh time of the memory devices fabricated on a polished silicon wafer is strongly affected by the crystal grown-in defects. Based upon the present results, the refresh time failure of the memory devices could be attributed to several types of crystal defects which include the D-defects produced as a result of vacancy aggregation during crystal growth and those associated with oxygen precipitation.