SEMICONDUCTOR MEMORY DEVICE WITH TRIPPLE WELL STRUCTURE AND METHOD OF MANUFACTURING THE SAME

摘要

A semiconductor memory device may include a semiconductor substrate that may have a first conductivity type. A first buried layer may be formed in the semiconductor substrate and may have a second conductivity type opposite to the first type conductivity. A first well may be formed on the first buried layer and may have the first type conductivity. A second well may be formed in the first well over a first surface portion of the first buried layer and may have the second conductivity type. A second buried layer may be formed in the first well and on a second surface portion of the first buried layer and may have the first conductivity type. A third well may be formed in the first well and on the second buried layer and may have the second conductivity type.