Appeal No. 95-1555
Application 07/871,530
In column 3, lines 15-28, Anderson further teaches that
Figures 2 and 3 shows the trench capacitors 16a and 16b extend
through P-tank 40 into the P substrate 48. Anderson further
teaches that on the outside of the trench capacitor walls, the
storage node material, arsenic, is implanted creating an
implanted arsenic layer 50. The arsenic layer 50 creates the N+
storage node of the trench capacitors. The upper portion of the
storage node on the top of the trench edge where the leakage
current could flow into the P-tank 40 is indicated by reference
numeral 51. Anderson teaches in column 3, lines 50-61, that the
P-tank 40 is implanted by an increased dopant over the p type
substrate 48. Anderson teaches that the purpose of the increased
dopant p-tank layer 40 is to control trench capacitance leakage
and latchup.
Tsuchiya is also concerned with trench capacitor type high
density dynamic random access memories. Thus, Tsuchiya’s trench
capacitor type high density dynamic random access memories are
subject to the same problems recognized by Anderson.
Those skilled in the art having both the teachings of
Tsuchiya and Anderson before them would have recognized from the
teachings of Anderson that it would have been desirable to use
the Anderson method of doping of the storage node and the
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