Semiconductor memory device with selection transistors with substrate penetrating gates

Abstract

A semiconductor memory device including a device isolation layer in a substrate to define first and second active portions, a first contact on the substrate, first and second memory cells spaced apart from the first contact in a first direction by first and second distances, respectively, first and second conductive lines connected to the first and second memory cells, respectively, and extending in a second direction, and first and second selection transistors respectively connected to the first and second conductive lines. A length of a bottom surface of a first gate electrode of the first selection transistor overlapping the first active portion in a third direction may be different from a length of a bottom surface of a second gate electrode of the second selection transistor overlapping the second active portion in the third direction.