Which option reflects a commonly cited hardware scalability challenge affecting Moore's Law?

• A. Quantum tunneling causing leakage as transistors shrink.
• B. Software updates slow down hardware improvements.
• C. Die size can always be reduced indefinitely.
• D. Economic costs of fabrication keep decreasing.

Answer: (A)

As transistors shrink, quantum effects become a practical barrier to continuing density increases. In particular, quantum tunneling allows electrons to leak through the thin insulating barriers inside a transistor. This leakage means devices draw more power even when they’re not switching, producing more heat and making it harder to keep performance gains without escalating power consumption. That leakage is a fundamental physical limitation tied to how small we can make features, and it directly challenges the pace at which transistor density—and thus Moore’s Law—can continue to improve.

Software updates slowing hardware improvements isn’t a hardware scaling issue; it’s about software and ecosystem pacing rather than the physical limits of chips. The idea that die size can be reduced indefinitely ignores real-world physical and manufacturing constraints, including leakage, variability, and yield. And the notion that fabrication costs keep decreasing overlooks the substantial, ongoing investments required for advanced lithography and fabs, which influence how quickly scaling can occur.