A semiconductor memory device includes a plurality of memory regions formed on one chip, each of the memory regions having a plurality of volatile memory cells that are formed with a density or capacity of 2̂K bits, where K is an integer greater than or equal to 0, and a plurality of input/output (I/O) terminals for inputting and outputting data of the volatile memory cells, and at least one peripheral region that controls a write operation for writing data into the memory regions and a read operation for reading data from the memory regions based on a command and an address input from outside. Thus, a total or entire density of the memory regions corresponds to a non-standard (or ‘interim’) density so that the semiconductor memory device may have an interim density.