China's YMTC wins patent battle against Micron in ongoing 3-year legal war over memory patents

A court in Germany has granted court injunctions against Micron, marking a win for YMTC on the European/German front in the 3-year legal war between the two companies over memory technology patents.

According to a Digitimes report, the court ruled on Sept. 18 that Micron did infringe YMTC’s 3D NAND technology patents in two instances. The injunctions could restrict Micron’s supply in Germany and impact the broader European NAND market. Micron said it disagreed with the court ruling and has already filed an appeal. It is also challenging the validity of the related patents in separate legal cases across various countries.

YMTC filed the lawsuit that won the recent injunctions in late 2025 at the Munich 1 Regional Court, opening five cases involving four German utility models and a European patent. The court granted injunctions on two of the utility models with 10-year protection periods — DE202020006166U1 (case No. 7O12615/25) and DE202021004551U1 (case No. 12614/25) — and adjourned the others. The injunctions are only first-instance rulings and can be suspended if Micron successfully appeals at the Munich Higher Regional Court.

The ruling is the latest development in a years-long dispute between the two memory makers that started in 2023 when YMTC sued Micron in California, alleging violations of eight 3D NAND architecture patents. The dispute has since snowballed into a multi-front war involving over 20 patents, with suits and countersuits on both sides. The cases cover patent infringement, declaratory judgment, spyware, libel, false advertising, and invalidation actions, and have been filed in courts across China, the U.S., the U.K., Germany, and in other parts of Europe.

Micron has vehemently denied any wrongdoing and has filed multiple patent invalidation challenges since 2024, the first of which came after YMTC dragged the company to court in China over related issues. Seven of the disputed patents have already been declared invalid, and Micron has said it will continue pushing to safeguard its intellectual property.

3D NAND is a flash-memory storage technology that stores data in products ranging from smartphones and SSDs to enterprise storage systems. Unlike older planar NAND, where memory cells are arranged side by side on a flat surface, 3D NAND stacks cells vertically in multiple layers, allowing manufacturers to pack more storage into a given area while increasing density and lowering cost per bit. Modern NAND chips can contain hundreds of these layers, making the architecture and manufacturing techniques behind them commercially valuable intellectual property.

The Micron-YMTC fight is playing out against the backdrop of the much larger technology dispute between the U.S. and China. Washington has tightened restrictions on China's access to advanced semiconductor manufacturing equipment and other chip technologies, while Beijing has placed export restrictions on many critical raw materials.

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