An asymmetrical lightly-doped source (ALDS) cell for virtual ground high density EPROMs

A novel EPROM (erasable programmable read-only memory) cell structure with asymmetrically doped source and drain junction suitable for virtual ground array architecture is described. The asymmetric cell nature eliminates a write disturbance of the adjacent cell in the write mode. In the read mode, the cell provides higher read current and substantial soft-write lifetime as a result of the selection of the lightly doped n/sup -/ region as the drain. The cell is implemented in virtual ground designs. A novel planarized process has been developed to improve the manufacturability. It is concluded that such scalable cell and array structures are promising for the next-generation high-density EPROMs in the 16-Mb regime.<>