Z-RAM

Zero-capacitor (registered trademark, Z-RAM) is a dynamic random-access memory technology developed by Innovative Silicon (defunct) based on the floating body effect of silicon on insulator (SOI) process technology. Z-RAM has been licensed by Advanced Micro Devices for possible use in future microprocessors. Innovative Silicon claims the technology offers memory access speeds similar to the standard six-transistor static random-access memory cell used in cache memory but uses only a single transistor, therefore affording much higher packing densities.

Details

Z-RAM relies on the floating body effect, an artifact of the SOI process technology which places transistors in isolated tubs (the transistor body voltages "float" with respect to the wafer substrate underneath the tubs). The floating body effect causes a variable capacitance to appear between the bottom of the tub and the underlying substrate, and was a problem that originally bedeviled circuit designs. The same effect, however, allows a DRAM-like cell to be built without adding a separate capacitor, the floating body effect taking the place of the conventional capacitor. Because the capacitor is located under the transistor (instead of adjacent to, or above the transistor as in conventional DRAMs), another connotation of the name "Z-RAM" is that it extends in the negative z-direction.