Assessment of Capacitorless DRAM Based on Stacked Nanosheet Feedback Field-Effect Transistors With Tree-Type Channel

In this study, a novel vertically stacked nanosheet (NS) feedback field-effect transistor with tree-type channel (Tree-FBFET) is proposed for one-transistor dynamic random access memory (1T-DRAM) application. Compared with the conventional NS channel structure, an additional SiGe interbridge (IB) channel is vertically integrated in Tree-FBFET. The enhanced performance of Tree-FBFET stems from additional SiGe storage region which is recognized as the SiGe channel. The Tree-FBFET based 1T-DRAM shows an improvement of 2.8 times in sensing margin (SM) (from 126 to$351~\boldsymbol {\mu }$A/$\boldsymbol {\mu }$m) and extends retention time (RT) from 0.6 to 32 s compared to 1T-DRAM based on conventional vertically stacked NS-FBFET. Moreover, the energy consumption is 35 fJ/bit for the write “1” operation and 0 fJ/bit for the hold operation. Geometric parameters of IB and NS, along with Ge mole fraction, are evaluated with respect to SM and RT. Furthermore, reliable$3\times 3$array operation of the proposed 1T-DRAM, free from disturbance of write operation, is also verified.