In a stack type memory cell of 8F.sup.2, bit line plug electrodes for connecting bit lines to source/drain diffusion layers of active regions in an area between two word lines WL are formed extend from the source/drain diffusion layers in parallel to the word lines WL and formed longer than the minimum element isolation width F and shorter than three times the minimum element isolation width F. Thus, a DRAM which uses stack type memory cells and whose integration density can be easily enhanced can be attained.