To provide a dynamic type semiconductor memory which can read out an initial data signal which are previously written, just after a power source is applied.

In a SDRAM source of a N channel MOS transistor included in a column selecting gate 13 is connected to a data input/output line IO or /IO based on an initial read-out data signal. Just after a power source is applied, storage nodes of all memory cells MC is at a 'L' level, an initial data signal of a logical level in accordance with connection relation between the memory cells MC and data input/output lines IO, /IO can be read out by selecting a desired memory cell MC.