United Microelectronics Corp. (UMC) has filed a lawsuit against Micron Technology subsidiaries in China for patent infringements.

Last month, Micron filed suit against UMC in the U.S.

UMC has been expanding its business in China, the world's largest and fastest growing semiconductor market. In addition to operating foundries in China, the company has licensed memory technology to various companies there.

"After conducting an in-depth review, UMC found that Micron's products sold in mainland China did indeed infringe upon the patent rights of the company, and thus patent infringement litigation has been pursued in order to obtain fair judgment," UMC said in a statement.

UMC said it is filing suit against Micron Semiconductor (Xi'an) Co. Ltd. and Micron Semiconductor (Shanghai) Co. Ltd. in the Fuzhou Intermediate People's Court of the People's Republic of China (PRC). The lawsuit covers three areas that allegedly infringe upon UMC's patent rights in China, including memory applications that relate to DDR4, SSD and memory used in graphics cards.

In the complaint, UMC has requested the court to order potential defendants to stop manufacturing, processing, importing, selling and intending to sell the allegedly infringing products, destroy all inventory and related molds and tools and demand that Micron compensate UMC for a total amount of RMB 270 million ($41.8 million) in damages.

Last December, Micron filed a civil suit in federal court in Northern California under the Defend Trade Secrets Act and civil provision of the Racketeer Influenced and Corrupt Organization Act against against UMC and China's Fujian Jinhua Integrated Circuit Co. (JHICC) alleging theft of its trade secrets and other misconduct.

JHICC has transferred technology from UMC and invested $5.65 billion in a local fab for memory production.

China is trying to enter the memory business. Last year, China announced a $24 billion memory project in central China's Wuhan city. Yangtze River Storage Technology (YRST), leading the effort, aims to build 3D NAND fabs. YRST is backed by China's Tsinghua Unigroup.

Tsinghua Unigroup has another DRAM and 3D NAND project in Nanjing. The total investment in both projects exceeds $54 billion.