A one transistor DRAM device includes: a substrate with an insulating layer, a first semiconductor layer provided on the insulating layer and including a first source region and a first region which are in contact with the insulating layer and a first floating body between the first source region and the first drain region, a first gate pattern to cover the first floating body, a first interlayer dielectric to cover the first gate pattern, a second semiconductor layer provided on the first interlayer dielectric and including a second source region and a second drain region which are in contact with the first interlayer dielectric and a second floating body between the second source region and the second drain region, and a second gate pattern to cover the second floating body.