Patent ID: 7965540
Filing Date: 2011-06-21
Classification: G11C,H01L,H03K

Abstract:
1. A static random access memory (SRAM) cell, comprising: cross coupled first and second complementary metal oxide semiconductor (CMOS) inverters formed on a semiconductor substrate, the CMOS inverters including a first storage node and a second storage node that is the logical complement of the first storage node; a first access transistor coupled between the first storage node and a true data bit line, and a second access transistor coupled between the second storage node and a complement data bit line, the first and second access transistors activated by a word line coupled to gate conductors thereof; both of the first and second storage nodes each further selectively coupled to a deep trench capacitor through a switching transistor, with the switching transistors controlled by a common capacitance switch line coupled to gate conductors thereof; the common capacitance switch line disposed directly above the deep trench capacitors at a first metal level, with the word line and true and complementary data bit lines disposed at a second metal level above the first metal level; wherein, in a first mode of operation, the switching transistors are rendered nonconductive so as to isolate the deep trench capacitors from the inverter storage nodes and, in a second mode of operation, the switching transistors are rendered conductive so as to couple the deep trench capacitors to their respective storage nodes, thereby providing increased resistance of the storage nodes to single event upsets (SEUs).