Long Retention of Gain-Cell Dynamic Random Access Memory With Undoped Memory Node

Low current leakage characteristics of a novel silicon-on-insulator (SOI) device are investigated in view of application to a gain-cell dynamic random access memory (DRAM). The device consists of a two-layered poly-Si gate. Since, in this device, the memory node is electrically formed by the gate in undoped SOI wire, no p-n junction is required. The retention is found to be dominated by the subthreshold leakage, which leads to long data retention. The device also achieved a fast (10 ns) writing time and its fabrication process is compatible with those of SOI MOSFETs. The present results, thus, strongly suggest a way of conducting a gain-cell DRAM to be embedded into logic circuits