Last week at the IEEE International Solid State Circuits Conference (ISSCC), two of the biggest rivals in advanced chipmaking, Intel and TSMC , detailed the capabilities of the key memory circuits, SRAM , built using their newest technologies, Intel 18a and TSMC N2 . Chipmakers' ability to keep scaling down circuits has slowed over the years-but it's been particularly difficult to shrink SRAM , which is made up of large arrays of memory cells and supporting circuits.
spectrum.ieee.org, Feb. 26, 2025 –
The two companies' most densely packed SRAM block provides 38.1 megabits per square millimeter, using a memory cell that's 0.021 square micrometers. That density amounts to as much as a 23 percent boost for Intel and a 12 percent improvement for TSMC . Somewhat surprisingly, that same morning Synopsys unveiled an SRAM design that achieved the same density using the previous generation of transistors , but it operated at less than half the speed.
The Intel and TSMC technologies are the two companies' first use of a new transistor architecture, called nanosheets . ( Samsung transitioned to nanosheets a generation earlier.) In previous generations, current flows through the transistor via a fin-shaped channel region . The design means that increasing the current a transistor can drive-so that circuits can operate faster or involve longer interconnects-requires adding more fins to the device. Nanosheet devices do away with the fins, exchanging them for a stack of silicon ribbons. Importantly, the width of those nanosheets is adjustable from device to device, so current can be increased in a more flexible fashion.
"Nanosheets seem to allow SRAM to scale better than in other generations," says Jim Handy , chief analyst at memory consulting firm Objective Analysis.
An SRAM cell stores a bit in a six-transistor circuit. But the transistors are not identical, because they have different demands on them. In a FinFET-based cell, this can mean building two pairs of the devices with two fins each and the remaining two transistors with one fin each.