Convex Channel Design for Improved Capacitorless DRAM Retention Time

A convex channel surface with Si_0.8Ge_0.2 is proposed to enhance the retention time of a capacitorless DRAM generation 2 type of capacitorless DRAM cell. This structure provides a physical well together with an electrostatic barrier to more effectively store holes and thereby achieve larger sensing margin as well as retention time. The advantages of this new cell design as compared with the planar cell design are assessed via two-dimensional device simulations. The results indicate that the convex heterojunction channel design is very promising for future capacitorless DRAM.