You can freely build on How Robert Dennard Invented the One-Transistor DRAM Memory Cell

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.

What is now free to use

All 0 claims of US 3387286 are in the public domain. Specifically:

The 0 dependent claims add narrowing limitations and are also free.

What is NOT covered

Patent expiry frees this specific invention. Separately-patented improvements made after expiry may still be protected.

• 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.

Who is building on this today

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.

Products built on expired version of this technology

How to cite this patent in your documentation

International Business Machines Corp. US Patent 3387286. Field-effect transistor memory. Granted 1968, expired 1987. Now in the public domain.

Note: This is a convenience citation. Consult a patent attorney for formal freedom-to-operate analysis.

PatentBrief is an educational resource and does not provide legal advice. Patent expiration information is derived from USPTO records and may not reflect continuation patents, divisional filings, or separately-patented improvements. For commercial use or production decisions, obtain a formal freedom-to-operate (FTO) opinion from a registered patent attorney.