A DRAM capable of realizing reduced power consumption, high-speed operation, and high reliability is provided. A gate electrode configuring a memory cell transistor of the DRAM is composed of an n-type polysilicon film and a W (tungsten) film stacked thereon. A part of the polysilicon film is embedded in a trench formed in a silicon substrate in order to elongate the effective channel length of the memory cell transistor. The other part of the polysilicon film is located above the trench, and an upper surface thereof is located above a surface of the silicon substrate (p-type well). Therefore, distances between the W film and a source and drain (n-type semiconductor regions) are ensured.