Exploring Electron Tunneling Transistors for Sub-1 nm Semiconductor Nodes
As traditional transistor designs approach the limits of atomic scaling, new approaches are needed to manage power, leakage and performance. Electron tunneling transistors are emerging as a leading option for sub-1 nm nodes, using quantum mechanical effects to enable switching at lower voltages. Erik Hosler, an expert in nanoscale device physics and lithography-based architecture, recognizes the need to move beyond thermionic transport to sustain progress in semiconductor scaling.
Unlike conventional MOSFETs that rely on energy barriers to regulate current flow, Tunneling Field Effect Transistors (TFETs) enable electrons to tunnel across a junction. This quantum behavior reduces supply voltage requirements and supports steeper subthreshold slopes, making TFETs a strong candidate for future low-power logic applications.
How Tunneling Transistors Work
In a TFET, the source and channel regions are engineered to create a steep band-to-band tunneling junction. When a gate voltage is applied, it modulates the tunneling probability between the valence band of the source and the conduction band of the channel. Electrons tunnel across this junction when the energy bands align, enabling current flow.
This mechanism differs fundamentally from thermionic emission over a barrier in MOSFETs. Tunneling provides sharp transitions between off and on states, leading to lower static and dynamic power consumption.
Various TFET architectures have been proposed, including vertical structures, nanowires and planar designs. Each offers unique tradeoffs in electrostatic control, manufacturability and performance under scaling. The challenge is to achieve a high current while maintaining subthreshold performance. Material selection, doping profiles and tunneling barrier engineering all play a role in optimizing device behavior.
Materials Driving Tunneling Performance
Materials with small band gaps and high tunneling probabilities are favored to maximize tunneling efficiency. Traditional silicon is not ideal for TFETs due to its relatively wide bandgap and low band-to-band tunneling rates. III-V semiconductors like Indium Arsenide and Gallium Antimonide offer much higher tunneling current densities. These materials support broken gap heterojunctions, where conduction and valence bands overlap to facilitate efficient carrier injection.
2D materials such as transition metal dichalcogenides are also being explored for their thin body control and favorable band alignments. Their atomic thickness and high electrostatic integrity make them suitable for short-channel tunneling devices. Device engineers are experimenting with heterojunction combinations and bandgap engineering to tune tunneling characteristics. Interface quality and defect control are critical to avoid trap-assisted leakage, which can degrade subthreshold behavior.
As TFETs approach commercialization, Erik Hosler notes, “The integration of emerging materials and advanced processes into CMOS technology is critical for developing the next generation of electronics.” That perspective highlights how material breakthroughs must align with established fabrication practices to support scalable, reliable tunneling devices within existing semiconductor infrastructure.
Integration With CMOS Platforms
While TFETs offer promising performance gains, they must be compatible with existing CMOS processes to support cost-effective deployment. This requires careful alignment with thermal budgets, process steps and interconnect architectures used in leading-edge logic.
One strategy is to build TFETs alongside traditional MOSFETs on the same die, creating hybrid architectures that balance performance and efficiency. In such designs, TFETs handle low-power logic, while MOSFETs provide drive strength for performance-critical paths. Another approach involves adapting Gate All Around (GAA) and nanosheet platforms to support TFET structures. These 3D form factors offer strong gate control and scalable geometries for tunneling devices.
Back-end integration challenges include contact resistance, parasitic capacitance and alignment between dissimilar materials. Process development must ensure yield and reliability comparable to established logic nodes. Efforts are underway to standardize TFET design libraries, simulation tools and characterization methods to accelerate adoption in advanced technology nodes.
Challenges in Scaling and Reliability
Despite their advantages, TFETs face several barriers to large-scale adoption. The most pressing issue is their low current compared to MOSFETs, which limits switching speed and drive strength in high-performance applications.
Material synthesis, doping uniformity and interface stability remain technical hurdles. Fabricating ultra-thin, defect-free heterojunctions at the wafer scale requires advances in epitaxy and metrology.
Variability in threshold voltage and subthreshold swing must be controlled to ensure predictable circuit behavior. This is particularly important in scaled technologies where variations can lead to functional failures or timing errors.
Reliability under stress, such as bias temperature instability and hot carrier injection, must be evaluated over extended operating lifetimes. These effects can degrade tunneling performance over time. Thermal management is also a consideration, as heat dissipation paths differ in tunneling devices. Proper heat sinking and package-level design will be required to prevent performance degradation.
Use Cases for Early Adoption
TFETs are well suited for applications that prioritize low power and long battery life over raw performance. These include ultra-low-power sensors, IoT devices and edge AI accelerators, where energy efficiency is paramount.
TFETs’ compact size and low leakage can benefit embedded systems and security chips, extending battery life and reducing thermal signatures. In implantable medical devices, low-voltage operation helps minimize tissue heating and power requirements.
At the system level, TFETs can be used in conjunction with MOSFETs to selectively reduce power in blocks that do not require high-speed operation. This partitioned approach enables gradual adoption and evaluation in real-world designs. Prototyping platforms are emerging that allow for circuit-level exploration of TFET behavior in functional logic paths, memory arrays and mixed-signal environments.
Looking Ahead to Beyond CMOS Logic
Electron tunneling transistors represent one of several paths beyond CMOS logic. Their ability to maintain switching behavior at low voltage and short channel lengths makes them candidates for post-1 nm technologies.
TFETs could be integrated with other emerging devices, such as ferroelectric FETs, spintronics and photonic logic, to create heterogeneous computing platforms optimized for specific tasks. Industry roadmaps now include TFETs as part of exploratory nodes, where their unique properties are evaluated alongside process cost and yield projections.
Standardization and ecosystem support will be essential to moving tunneling devices from lab-scale demonstrations to high-volume production. Collaborative development between foundries, toolmakers and circuit designers will play a critical role.
Powering the Next Leap in Device Scaling
Tunneling transistors offer a fundamentally different approach to switching, one that aligns with the quantum limits of miniaturization. As traditional field-effect transistors reach their practical boundaries, TFETs provide a viable path forward for sub-1 nm scaling.
By controlling electron flow through tunneling rather than thermionic emission, these devices achieve steep subthreshold slopes and operate at lower voltages, addressing both power and size challenges.
Their success will depend not only on performance metrics but also on integration feasibility, process maturity and long-term reliability. If these challenges are met, TFETs could form the backbone of future logic architectures in which energy efficiency is no longer a constraint but a competitive advantage.
