'Mirrorbit'/'Strataflash' for DRAM?
To do something like strataflash, you'd have to have multiple voltages stored on the capacitor. You'd have to refresh the capacitor more often, since you'd have less margin between the possible states (assuming you can even detect the "clean" states properly - I think DRAMs are sensed and have low-swing bitlines already). I don't know enough about Mirrorbit to understand how it would apply at all to DRAM.
*Not speaking for any company