Comparing FinFETs vs. GAAFETs

Key Takeaways

• FinFET technology utilizes fin-shaped FETs and offers various benefits such as low leakage currents, high drive currents, and fast switching times.

• In GAAFET construction, the channel is lifted up and offers the possibility to vary the channel width as per the requirements of the transistor type in use. 

• Nanosheet-based GAAFETs provide a larger drive current compared to finFET technology.

During the mid 20th century, complementary metal-oxide semiconductors (CMOS) were a remarkable invention for the electronics industry. CMOS technology started the trend of miniaturization and performance enhancement in semiconductor electronics, especially in integrated circuit applications. CMOS technology introduced planar transistors with low costs, low power consumption, and high packing density. The downsizing of planar transistors continued with advanced manufacturing processes. However, the scaling of CMOS planar transistors brought numerous problems such as gate leakage currents, short channel effects, quantum tunneling leakage, variability, mobility degradation, etc.

The development of multigate devices such as finFETs and GAAFETs are innovations in transistor technology that offset planar transistors. FinFET technology emerged as a solution for planar transistor-induced problems by opening the scope for three-dimensional (3D) transistor construction. GAAFETs confirm 3D technology in semiconductor transistor fabrication and help overcome the limitations of finFET. In this article, we will compare finFET vs. GAAFET technologies. 

Multigate Devices: FinFETs and GAAFETs

The evolution of the three-dimensional configuration of transistors resolved the issues brought about by planar transistor technology. 3D structured transistor construction focused on establishing the channel’s gate on three sides, thereby increasing the gate surface area. The increase in the surface area, in turn, increased control over the electrostatics in multigate devices.  FinFET technology introduced one such multigate device that utilized fin-shaped FETs with various benefits such as low leakage currents, high drive currents, fast switching times, etc. In finFETs, the channel's control increases with the downsizing of the transistor and gives superior scalability property to the fin-based transistor device fabrication.

FinFET technology revolutionized the production of computer processors and memory units with its high computational speed and smaller dimensions. With the demand for miniaturized, high-speed computer processors, finFET technology evolved from 22nm to 3nm nodes. The transition from 22nm to 16nm nodes provoked chip manufacturers to shift from planar transistor technology to finFET technology. However, the 5nm and 3nm finFET generations experienced poor control over leakage currents and faced several short channel effects. To further downsize, finFET technology became obsolete and a new transistor technology became popular: gate-all-around transistors (GAAFETs). 

Among the finFET successors, GAAFETs exhibited high potential for further downsizing of transistors while offering better capabilities. In GAAFET construction, the channel is lifted up when compared to FinFET construction and opens the possibility to vary the channel width as per the requirements of the transistor type in use. Let’s compare finFETs and GAAFETs a little further. 

FinFETs vs. GAAFETs

FinFETs and GAAFETs utilize a non-planar transistor structure that increases the speed and performance of devices with reduced power consumption and footprint. Here are a few ways in which finFETs and GAAFETs can be compared.

Internal Structure

In finFETs, the device’s internal structure is developed such that the gate surrounds three sides of the channel. Contrary to finFET technology, in GAAFETs, the gate encloses the entire channel, which is how these transistors got their name. Nanowire or stacked nanosheet technology is employed in GAAFETs, which gives the advantages of a raised channel and channel width scalability. 

Production

Both finFETs and GAAFETs can be mass-produced using the same process tools and manufacturing methods. When chip manufacturers shifted to new gate-all-around transistor technologies, they did not have to invest in new processes or manufacturing equipment. The easy transition from finFET to GAAFET fabrication reduced costs and allowed manufacturers to quickly implement these new technologies.

Footprint Area and Speed

In finFETs, additional fins are required to increase device speed. The process of adding parallel fins increases the footprint area, and this limits the need for speed in finFETs with downsizing. The stacking of nanosheets is replacing traditional fins in GAAFETs. Nanosheets are usually stacked vertically, which eliminates the need for more area. In GAAFETs, higher speed is achieved within smaller transistors overall size when compared to finFETs. 

High Drive Currents

Currently, stacked nanosheets are trending in GAA technology. Nanosheet-based GAAFETs provide a larger drive current for the given footprint compared to fin technology. The stacking of nanosheets creates larger effective channel width and increases the device drive current capability compared to finFETs.

Low Leakage Currents, Operational Voltage, and Dynamic Power

As the gate surrounds only three sides of the channel in finFETs, one side is left without gate control. When the gate length is reduced in finFETs, it creates short channel effects and more leakage currents through the ungated side of the device. However, in GAAFETs, all sides of the channel are enclosed by gate material. Enclosing the channel by the gate in GAAFET increases the channel control, reduces leakage currents, and brings down the operational voltage and dynamic power.

By comparing finFET vs. GAAFET technologies, it can be summarized that gate-all-around transistors are the future of integrated circuits. Their design flexibility, low operational voltage, high drive currents, high computational speed, and excellent performance within a smaller footprint area will continue to make them advantageous. Cadence software can help you design integrated finFET or GAAFET-based integrated circuits.

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