Nonvolatile memory technologies — mask ROM implementation Mask ROM (factory-programmed ROM) is typically implemented using which underlying technology?

Introduction / Context:
Mask ROM is a read-only memory whose contents are defined during semiconductor fabrication via photolithographic masks. Recognizing its base technology helps differentiate it from programmable alternatives like PROM, EPROM, and Flash.

Given Data / Assumptions:

• Modern integrated memories are fabricated on silicon using MOS (metal–oxide–semiconductor) processes.
• Historical, board-level diode matrices existed but are not the mainstream IC implementation.
• Mask ROM stores bits by the presence/absence of connections or transistors laid out at manufacture time.

Concept / Approach:
The term “mask ROM” derives from the photomask patterning used to create fixed data. In current practice, these arrays are realized as MOS transistor structures or hardwired connections formed within a MOS process node. Diode matrices are educational or very old implementations and not reflective of standard IC mask ROM today.

Step-by-Step Solution:
Identify mainstream IC process: CMOS/MOS.Recognize mask-defined connectivity in MOS arrays.Conclude that mask ROM is implemented using MOS technology.

Verification / Alternative check:
Fabrication flow and foundry process design kits (PDKs) for ROM macros target CMOS/MOS rules. Vendor datasheets for embedded ROM in microcontrollers also list CMOS processes and geometries (e.g., 180 nm, 90 nm, etc.).

Why Other Options Are Wrong:

• Diode or resistor–diode technology: Not typical for monolithic, high-density modern ROM ICs.
• DROM technology: Not a standard term for fabrication technology.

Common Pitfalls:

• Confusing legacy diode matrices with integrated mask ROM implementations.
• Assuming “ROM” implies a specific device package or programming method instead of a fabrication-defined array.

Final Answer:
MOS technology