Hi,
the schematic unit cell in DRAM is drawn below:
https://docs.google.com/file/d/0BzvjZoZeQg3nd1JYNTdGOTdIS2c/edit?usp=sharing
Here, "zero" or "one" are simply capacitor charged or not. So to write a bit, we attach (or not) a source (Vcc) voltage with switch WBIT.
In the case of FeRAM, we...