Toshiba Corp. and Western Digital Corp., its U.S. partner, will invest a total of over ¥1 trillion in the three years from fiscal 2016 to increase production of a new type of flash memory, sources said Tuesday.

Toshiba and flash memory maker SanDisk Corp., which was bought by hard disk drive manufacturer Western Digital in May, jointly ran and shared investment in a factory in Yokkaichi in Mie Prefecture. Western Digital plans to continue investment in the plant even after the acquisition.

Toshiba is planning to invest about ¥860 billion over the three-year period and Western Digital's investment is likely to match that of the Japanese firm, the sources said.

Flash memory chips are used in a range of digital devices such as smartphones. The new type of memory will significantly expand the volume of data that can be stored.

South Korean and other foreign rivals are also stepping up investment in the business as flash memory is expected to be used for a wider variety of purposes.