Shared Trench One-Device Dynamic Random-Access Memory Cell
Original Publication Date: 1988-Dec-01
Included in the Prior Art Database: 2005-Feb-15
Within a single trench in a silicon substrate, complete structure for two one-device dynamic random-access memory (DRAM) cells and their individually accessible word, bit and plate lines is constructed. Referring to the figure, isolation trenches 2 are first etched in the silicon substrate 4 and then filled with an insulator. Device trenches 6 are next etched orthogonally to the isolation trenches 2. A thin N+ dopant source 8 is next deposited by a conformal deposition process and is etched back by reactive ion etching (RIE) to leave only the lower 3/5 of the vertical trench walls coated with dopant source 8. Device source diffusions 10 are formed by diffusion of the N+ dopant from sources 8 into substrate 4 and an oxide 12 is grown. The trench is then filled with a conductor 14, e.g.