A semiconductor storage device includes a memory cell transistor and a selective transistor formed on a semiconductor substrate, a first interlayer insulating film which is formed on the semiconductor substrate, an insulating layer formed by use of a material higher in dielectric constant than the first interlayer insulating film, a contact plug which penetrates the insulating layer and the first interlayer insulating film and which is electrically connected to a drain of the selective transistor, and a bit line which is in contact with the contact plug. A partial region in the bottom surface of the bit line is located lower than the upper surface of the contact plug, and is in contact with the surface of the insulating layer, and the partial region is also in contact with the side surface of the contact plug.