Fabrication method of a read-only semiconductor memory device

Details Fabrication method of a read-only semiconductor memory device Fabrication method of a read-only semiconductor memory device

1994-10-06

1995-11-28

Chaudhuri, Olik

Fishing, trapping, and vermin destroying

437 48, 437 52, 437 47, H01L 21265

Patent

active

054707749

ABSTRACT:
A fabrication method of a semiconductor memory device in which the punch-through phenomenon is difficult to occur in uncoded or unwritten memory cells. First impurity-doped regions for coding are formed in channel areas of selected ones of first MOS transistors in the memory cell area, using a patterned photoresist film as a mask, respectively. Second impurity-doped regions for threshold adjustment are formed in channel areas of unselected ones of the first transistors and second transistors in the peripheral circuit area, using a patterned photoresist film as a mask, respectively. During the process of forming the second impurity-doped regions, the dopant doped for threshold adjustment through the selected ones of the first transistors into the substrate forms third impurity-doped regions apart from the channel areas of the selected ones of the first transistors, respectively. The third impurity-doped regions serve to restrain the first dopant doped into the selected ones of the first transistors from laterally diffusing in the substrate, preventing the punch-through phenomenon.

REFERENCES:
patent: 5063170 (1991-11-01), Okuyama
patent: 5200355 (1993-04-01), Choi et al.
patent: 5275959 (1994-01-01), Kobayashi et al.

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