Promising another leap in system performance, IBM said yesterday that it has developed a transistor with two gates instead of one, allowing it to operate at up to twice the speed of today's conventional transistors.

The 'double-gate' transistor, expected to show up in microprocessors in about five years, can also be produced in a much smaller size than transistors used today, which means more transistors can be packed together on a chip, said IBM.

Transistors are the basic building block of microchips. The devices act like tiny switches with a 'gate' that controls the flow of electrons. Shrinking of transistors has been the foremost way of increasing chip performance and meeting Moore's Law, the principle that says the number of transistors on a chip will double every 18 to 24 months.

"If you keep shrinking [the size of transistors] like the industry has done in the past, we would have had transistors that never shut off and electrical leakage," said Aidan Kelly, manager of IBM's custom logic design centres in Europe. "The double-gate transistor represents a design change, delivering better performance at a smaller scale."

The performance of chips largely depends on the ability of the millions of transistors to switch on and off quickly and completely with the least amount of energy, he said.

AMD has also made a transistor breakthrough. Yesterday it announced that it's developed a transistor with a gate length of 15 nanometres (0.015-micron) that can switch more than three trillion times per second.

This transistor is more than five times as compact as transistors in existing commercial chips, which have gate lengths of just under 100 nanometres (0.1 microns). The development of a transistor with a 15-nanometre gate length is important if semiconductor manufacturing technology is to keep moving forward.

Transistor gate length is related to, but not equivalent to, the commonly used measure of process size. The most advanced current technology has a process size of 0.13 microns, which means the lines and spaces on the chip's surface are 0.13 microns apart. The transistor gate lengths must be shorter than that to fit inside the lines, and current commercial chips use devices with gate lengths of around 0.1 micron.

By creating a much smaller basic building block for chips, AMD's 15-nanometre transistor heralds the way towards the development of faster and more complex microprocessors.