Well, it looks there's a new challenger about to enter that ring; double floating-gate field effect transistors, currently in prototype form at North Carolina State University. Whereas the single floating-gate variety is currently responsible for the flash memory in your USB keys and SSDs, the second floating gate lets bits of data stay in an active, ready state, but the computer can also apply a higher voltage to "freeze" them in place. Since the memory can switch between static and dynamic modes in a single cycle and the data never disappears in between, researchers imagine the new tech could lead to instant-on computers and power-saving techniques that shut down idle memory banks.
In operation, computers using the double floating-gate FETs for their main memory can operate normally until they become idle, at which time their data values can be transferred to the second gate in order to power down the memory chip. Then when the stored values need to be accessed again by the computer, the second gate quickly transfers their stored charge back to the first gate and normal operations can resume.
"We believe our new memory device will enable power-proportional computing, by allowing memory to be turned off during periods of low use without affecting performance," said Franzon.
So far the researchers have only built the gate structures in their new FET design and are currently performing cycling testing to make sure that memories stored and retrieved from the floating gates do not cause fatigue that could eventually wear out the devices. Flash, for instance, uses voltages so high during hot-carrier injection that devices can only survive about 10,000 read/write cycles. Double floating-gate FETs use lower voltages, but only cycling testing can determine whether the devices experience excessive fatigue.
If the test devices pass cycle testing, then the researchers' next step will be to fabricate real semiconductor memories out of them—a task the researchers hope to perform by next year. Also working on the project was Neil Spigna, a research assistant professor at NC State and doctoral candidates Daniel Schinke and Mihir Shiveshwarkar. Funding was provided by the National Science Foundation.