MoS2, the "ultimate thin" semiconductor material poised to succeed silicon. Creating uniform monolayer films across entire wafers has long been considered impossible. Now, researchers from Japan's NIMS and the University of Tokyo have achieved wafer-scale deposition of films just three atoms thick, marking a significant step forward in next-generation semiconductor technology.

Silicon's Limits and the Quest for Next-Generation Semiconductors

Semiconductor miniaturization has followed Moore's Law for decades, but conventional silicon-based technology is approaching fundamental physical limits. At today's cutting-edge 2-3nm process nodes, transistor channels are only a few nanometers thick, making quantum tunneling effects and leakage currents increasingly problematic.

Major semiconductor companies like TSMC, Intel, and Samsung are accelerating research into alternative materials for the post-silicon era of the 2030s and beyond. The leading candidates are two-dimensional materials known as transition metal dichalcogenides (TMDs).

What Is Molybdenum Disulfide (MoS2)?

MoS2 (molybdenum disulfide) is a representative TMD material. A monolayer of MoS2 consists of a layer of molybdenum (Mo) atoms sandwiched between two layers of sulfur (S) atoms, a sandwich structure with an ultimate thickness of only about 0.65nm, just three atoms thick.

Traditionally, MoS2 has been used industrially as a lubricant. Its layered structure, held together by weak van der Waals forces between layers, allows the layers to slide easily, resulting in a low friction coefficient. However, researchers recently discovered that when reduced to a monolayer, this material becomes a direct bandgap semiconductor with excellent electrical properties.

Monolayer MoS2 has a bandgap of approximately 1.8eV and can achieve high on/off ratios and electron mobility, ideal characteristics for next-generation ultra-low-power devices.

A Technical Breakthrough Through Industry-Academia Collaboration

On January 21, 2026, a research group led by Yoshiki Sakuma, NIMS Distinguished Researcher at the National Institute for Materials Science (NIMS), and Professor Kosuke Nagashio from the University of Tokyo's Graduate School of Engineering published their results in Nature Communications. The collaborative research included Nagoya University, the University of Tsukuba, and semiconductor equipment giant Tokyo Electron Technology Solutions.

The research team discovered two critical mechanisms when growing monolayer MoS2 using metalorganic chemical vapor deposition (MOCVD):

Self-alignment mechanism: MoS2 crystal grains growing on sapphire substrates spontaneously align their crystal orientations as they merge, ultimately forming a single crystal.

Self-limiting mechanism: Using uniquely selected precursors (source gases), the deposition reaction automatically stops at monolayer thickness.

Through the synergistic effect of these two mechanisms, the team achieved uniform and reproducible epitaxial growth of monolayer MoS2 across entire 2-inch sapphire wafers.

Quality Verification: Electron Mobility Evaluation

The researchers evaluated film quality through temperature-dependent electron mobility measurements. In high-quality semiconductors, lower temperatures reduce lattice vibrations (phonons), suppressing electron scattering and increasing mobility. In contrast, materials with many defects show defect-dominated scattering, limiting mobility improvements even at low temperatures.

Measurements confirmed that MoS2 films produced by this method showed significantly improved mobility at lower temperatures, demonstrating extremely low defect density and confirming the formation of high-quality single-crystal films.

The Technology Industry Has Been Waiting For

What makes this achievement significant is its "wafer-scale" nature. While laboratory methods like mechanical exfoliation (the "scotch tape method") can produce high-quality monolayer MoS2, they only yield micrometer-sized flakes, completely unsuitable for large-scale integrated circuit manufacturing.

The semiconductor industry has established processes for forming uniform thin films on large-diameter wafers (200-300mm) and batch-processing thousands to tens of thousands of chips simultaneously. While this research uses 2-inch (approximately 50mm) wafers, it demonstrates uniform film formation across entire wafers using MOCVD, a method compatible with industrial manufacturing processes.

Tokyo Electron's participation in this collaborative research underscores the high expectations for industrializing this technology.

The Path to Sub-1nm Node Transistors

Current cutting-edge semiconductors are at the 3nm node, but the industry is pushing for further miniaturization. TSMC plans to begin mass production of its 1.6nm node (A16) by late 2026, with "sub-1nm nodes" on the horizon beyond that.

At sub-1nm nodes, transistor channel thickness reaches extreme limits where conventional silicon cannot suppress electron tunneling. Monolayer MoS2, functioning as a semiconductor at just 0.65nm thick, emerges as a leading candidate material for realizing sub-1nm node logic transistors.

Remaining Challenges and Future Outlook

Several challenges remain before this technology reaches commercialization.

First, wafer size scaling, expansion to 300mm wafers standard in industry is necessary. Additionally, interface control between MoS2 and metal electrodes, realization of p-type semiconductors (not just n-type), and integration with existing CMOS manufacturing lines are critical issues.

However, the discovery of the "self-alignment" and "self-limiting" mechanisms provides essential foundational technology for addressing these challenges. The research group states that this achievement will significantly contribute to future large-scale integrated circuits, low-power electronics, and optoelectronic device applications.

Japan's Materials Science Leading the World

This research showcases Japan's strengths in materials science. NIMS is one of the world's premier materials research institutions, and collaboration between universities like the University of Tokyo and Tokyo Electron, a leading equipment manufacturer, made this achievement possible.

While Japan's presence in the semiconductor industry has declined in recent years, it maintains world-class technological capabilities in materials and manufacturing equipment, the "unsung heroes" of the industry. How Japan's fundamental research will shape the future of next-generation semiconductors remains a story worth watching.

In Japan, research into next-generation semiconductor materials that surpass silicon's limits continues to advance steadily. This technology could determine the future of the semiconductor industry. Is similar research being conducted in your country? What are your thoughts on next-generation semiconductor materials and the efforts being made where you live? We'd love to hear your perspectives.

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