Method for making a dual trench capacitor structure

摘要

A dual trench structure for a high density trench DRAM. The dual trench structure, each of which can reside in part under the access device of a respective cell, does not require the use of expensive selective epi growth techniques. A sub-minimum lithographic trench opening can be used (1) to improve the cell area, (2) to increase the device length, and (3) to improve the margin of diffusion straps. Acceptable trench capacitance for the cells formed in a single opening can be achieved either by using thin capacitor dielectric, or by expanding the trenches laterally under the devices.