A random access read/write MOS memory device employs an array of rows and columns of dynamic memory cells which are accessed by multiplexed row and column addresses latched in by row address strobe and column address strobe signals. For refresh operations, only the row address is needed, so no column address strobe occurs. During long periods of refresh-only operations, deterioration of internal clocks based on the column address strobe signal is avoided by boosting these clocks from the row address strobe signal.