Plant shutdowns in Japan have halted production in factories accounting for 25 percent of the world’s silicon wafers used to make computer chips, according to a report released Monday by the research firm IHS iSuppli.

The Shin-Etsu plant, according to IHS iSuppli, produces 20 percent of the raw wafers used by semiconductor makers worldwide.

Another shuttered wafer factory in Utsunomiya, owned by MEMC Electronic Materials Inc., accounts for 5 percent of global wafer supply, the report said.

The semiconductor category hit hardest, the report said, will be memory, including flash memory.