Mask-Programmable Read Only Memory with Electrically Isolated Cells

A new patent filed by inventor Lim, Mingyu, on November 22, 2021, has been published online, detailing a mask-programmable read only memory (ROM) with electrically isolated cells. The patent, number 12432912, was published on September 30, 2025, and is assigned to SK keyfoundry Inc. This innovative design addresses the limitations of traditional semiconductor memory devices by introducing a novel approach to electrically isolate cells in a mask ROM.

Key Takeaways:

• The patent proposes a mask-programmable ROM with a first unit cell and a second unit cell, each comprising a source contact, a bit line contact, and a gate electrode.
• The novel aspect of this design lies in the electrically isolated cells, achieved through the use of an isolation gate electrode and a via structure connecting the second bit line contact to the bit line.
• The isolation gate electrode is formed in the same operation as the gate electrodes and is connected to a ground potential, ensuring optimal performance and reducing power consumption.
• The ROM also includes a first metal wiring and a second metal wiring, each overlapping with a portion of the gate electrodes, but not fully crossing them. This allows for efficient data storage and retrieval.
• The design enables the simultaneous storage of data in the first unit cell and the second unit cell, making it suitable for high-density memory applications.
• The inventor suggests various modifications, including the use of a first source line and a second source line, and adjusting the width of the via structure and the second bit line contact.

Statistics:

• Patent number: 12432912
• Filing date: November 22, 2021
• Publication date: September 30, 2025
• Patent owner: SK keyfoundry Inc.
• Description of the invention: A mask-programmable ROM with electrically isolated cells, comprising:

+ A first unit cell and a second unit cell

+ An isolation gate electrode, configured to isolate the first unit cell and the second unit cell

+ A bit line, configured to cross the first unit cell and the second unit cell

+ The first unit cell comprising a first source region, a first drain region, a first gate electrode, a first source contact, a first bit line contact, and a first metal wiring

+ The second unit cell comprising a second source region, a second drain region, a second gate electrode, a second source contact, a second bit line contact, and a second metal wiring

• Total claims: 12
• Date and time of patent issue: September 30, 2025 12:00 AM

Sources:

• Lim, Mingyu. Mask-programmable read only memory with electrically isolated cells. U.S. Patent Number 12432912, filed November 22, 2021, and published online on September 30, 2025. Patent URL (for desktop use only): https://ppubs.uspto.gov/pubwebapp/external.html?q=(12432912)&db=USPAT&type=ids