for computer memory in the 1980s.

The two most common types of DRAM memory cells since the 1980s have been trench-capacitor cells and stacked-capacitor cells. Trench-capacitor cells are where holes (trenches) are made in a silicon substrate, whose side walls are used as a memory cell, whereas stacked-capacitor cells are the earliest form of three-dimensional memory (3D memory), where memory cells are stacked vertically in a three-dimensional cell structure. Both debuted in 1984, when Hitachi introduced trench-capacitor memory and Fujitsu