AnandTech report MIFS has two 300mm fabs, with an output of 28,000 to 40,000 300mm wafers per month. This is a big upgrade versus the 140,000 300mm wafers per month capacity that UMC currently has. However, the MIFS fabs date back to 2004 and 2006 and have never seen serious investment. They're still on a mature 40nm node.
MIFS runs two 300-mm fabs — the Fab-B1 and the Fab-B2 constructed in 2004 and 2006, respectively. Both fabs were built by Fujitsu to produce chips using 90 nm and 65 nm process technologies and have never been seriously upgraded. In 2009 the company decided to go “fab lite” and spun off the fabs into Fujitsu Semiconductor Limited, which started to outsource production of 28-nm and 40-nm chips to TSMC, which was reportedly interested in taking over the plants. In 2014 Fujitsu Semiconductor agreed to form a joint venture with UMC and sell a stake in MIFS to the Taiwanese contract maker of chips. In return, UMC licensed its 40 nm process technology to MIFS and even helped to install an appropriate production line in one of the fabs.