Recently, one-transistor dynamic random-access memory (1T-DRAM) cells having a polysilicon body (poly-Si 1T-DRAM) have attracted attention as candidates to replace conventional one-transistor one-capacitor dynamic random-access memory (1T-1C DRAM). Poly-Si 1T-DRAM enables the cost-effective implementation of a silicon-on-insulator (SOI) structure and a three-dimensional (3D) stacked architecture for increasing integration density. However, studies on the transient characteristics of poly-Si 1T-DRAM are still lacking. In this paper, with TCAD simulation, we examine the differences between the memory mechanisms in poly-Si and silicon body 1T-DRAM. A silicon 1T-DRAM cell’s data state is determined by the number of holes stored in a floating body (FB), while a poly-Si 1T-DRAM cell’s state depends on the number of electrons trapped in its grain boundary (GB). This means that a poly-Si 1T-DRAM can perform memory operations by using GB as a storage region in thin body devices with a small FB area.

Capacitorless DRAM (1T-DRAM) is considered to be a promising candidate to replace conventional 1T-1C DRAM which is facing a scaling limit. 1T-DRAM with a poly-Si body has attracted much attention specifically for its simple SOI fabrication and stackable memory which allow for ultrahigh density. A single crystal silicon-based junctionless (JL) transistor is unsuitable for a 1T-DRAM cell because the transistor’s body is too thin to have a storage region and its junction barrier is too low to store holes. In contrast, a JL transistor with a thin poly-Si body can be used as a 1T-DRAM cell because it uses a grain boundary as its charge storage region instead of a floating body. We carried out intensive simulations of JL transistors with poly-Si body and confirmed the possibility of using a JL structure as a poly-Si 1T-DRAM cell. In addition, we analyzed the memory mechanism and characteristics of this structure.