How Robert Dennard Invented the One-Transistor DRAM Memory Cell
IBM's 1967 patent for a memory cell using a single transistor and a capacitor, which became the foundation for all modern computer RAM.
Original patent title: “Field-effect transistor memory”
IBM's 1967 patent for a memory cell using a single transistor and a capacitor, which became the foundation for all modern computer RAM. Granted to International Business Machines Corp in 1968 with 191 forward citations, and it is now in the public domain.
Key facts
Coverage
What does this patent actually cover?
This patent describes a memory cell that stores a single bit of data using only one field-effect transistor and one capacitor. Before this, computer memory required multiple transistors per bit, which made it bulky, expensive, and power-hungry. By shrinking the design to a single transistor, this invention allowed engineers to pack millions of bits of data into a tiny silicon chip. When the transistor is activated, it allows a charge to be stored in the capacitor, representing a one or zero.
The gap
What does this patent NOT cover?
- Does not cover static RAM (SRAM) which uses multiple transistors to hold data without needing periodic refreshing.
- Does not cover the manufacturing processes for etching these transistors onto silicon wafers.
- Does not cover magnetic core memory or other non-semiconductor storage technologies.
These exclusions are unique to PatentBrief — derived from the actual claim language, not patent-office boilerplate.
What made this novel
By realizing that a capacitor could hold a charge for long enough to be useful if refreshed periodically, Dennard eliminated the need for complex, multi-transistor flip-flop circuits for every single bit of storage.
The Patent Drawing
Schematic visualization of the patent's claim structure. Hand-drawn diagrams in progress for each landmark patent.
Where you've seen this
Real-world examples
DDR4 and DDR5 RAM sticks in desktop PCs
LPDDR memory modules in smartphones
Embedded DRAM in gaming consoles
Why it matters
The bigger picture
This invention is the reason your computer or smartphone can have gigabytes of memory. It enabled the transition from room-sized computers to the personal computing era by making high-density memory affordable and reliable. It remains the standard architecture for Dynamic Random Access Memory (DRAM) used in almost every electronic device today.
Filed
July 14, 1967
Granted
June 4, 1968
Market context
Who's building on this
Companies in this space
Major semiconductor manufacturers like Samsung, SK Hynix, and Micron continue to refine this fundamental architecture to achieve higher densities and faster speeds. While the original patent has long expired, the basic principle of the one-transistor, one-capacitor cell remains the industry standard.
Market impact
This patent triggered a massive shift in the computing industry, enabling the production of dense, low-cost memory chips. It effectively killed off older, slower technologies like magnetic core memory and paved the way for the microprocessor revolution of the 1970s and 80s.
Claim 1 — Plain English
What this patent covers
This patent describes a memory cell that stores a single bit of data using only one field-effect transistor and one capacitor. Before this, computer memory required multiple transistors per bit, which made it bulky, expensive, and power-hungry. By shrinking the design to a single transistor, this invention allowed engineers to pack millions of bits of data into a tiny silicon chip. When the transistor is activated, it allows a charge to be stored in the capacitor, representing a one or zero.
The clever bit
By realizing that a capacitor could hold a charge for long enough to be useful if refreshed periodically, Dennard eliminated the need for complex, multi-transistor flip-flop circuits for every single bit of storage.
What it does not cover
- Does not cover static RAM (SRAM) which uses multiple transistors to hold data without needing periodic refreshing.
- Does not cover the manufacturing processes for etching these transistors onto silicon wafers.
- Does not cover magnetic core memory or other non-semiconductor storage technologies.
Patent Journey
From filing to expiry
PatentBrief Score
Impact Score
Moderate
Citation count
40/40
Highly cited
Claim breadth
0/20
Narrow claimsclaimsThe numbered statements at the end of a patent that legally define what the inventor owns.Read more →
Recency
0/20
Older than 20 years
Assignee scale
0/20
Independent or smaller assigneeassigneeThe entity that owns the patent — usually the inventor's employer or a company.Read more →
PatentBrief Impact Score — based on citation count, claim breadth, recency, and assignee scale. Not a legal assessment.
Heuristic Value Estimate
What this patent might be worth
$42K – $134K
Midpoint $84K · expired or expiring · industry ×1.4
Heuristic only — blends forward/backward citation counts, claim scope, time remaining, litigation history, and CPC-derived industry baseline. Real valuations need a professional appraisal.
Concepts involved
Citations
Patent lineage
Cite this patent
Dennard, R. H. (1968). How Robert Dennard Invented the One-Transistor DRAM Memory Cell (U.S. Patent No. 3,387,286). U.S. Patent and Trademark Office. https://patentbrief.org/patent/us/3387286/dram-memory-dennard
Auto-generated from the patent record. Double-check author order and the issue date against the official USPTO document before submitting.
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Common Questions
Frequently Asked Questions
What does How Robert Dennard Invented the One-Transistor DRAM Memory Cell cover?
IBM's 1967 patent for a memory cell using a single transistor and a capacitor, which became the foundation for all modern computer RAM.
Who owns patent US 3387286?
International Business Machines Corp owns this patent, granted in 1968.
When does this patent expire?
This patent has expired and is now in the public domain — anyone can use the invention freely.
What is patent US 3387286 cited by?
This patent has been cited by 191 later patents that build on its ideas.
What problem does this patent solve?
This invention is the reason your computer or smartphone can have gigabytes of memory. It enabled the transition from room-sized computers to the personal computing era by making high-density memory affordable and reliable. It remains the standard architecture for Dynamic Random Access Memory (DRAM) used in almost every electronic device today.
What does this patent NOT cover?
Does not cover static RAM (SRAM) which uses multiple transistors to hold data without needing periodic refreshing.
Same assignee
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