In a deal worth a reported 500 billion yen ($4.84 billion) the companies will build a factory to make flash memory consisting of several layers of semiconductors stacked together to give as much as a terabyte 1,000 gigabytes of storage.
That is around 16 times bigger than the largest 64-gigabyte Toshiba memory currently available in smart phones and tablet devices.
Toshiba will demolish its existing plant in Japan to build a new facility that will house production apparatus using technologies from both firms and which the firms hope will start operating in 2016, a statement said.
"In about five years (from the planned start of the factory), we would like to produce one-terabyte products," said a Toshiba spokeswoman.
The plan comes at a time of increasing competition among the world's technology firms to meet demand for ever-higher capacity memory chips for consumers increasingly using mobile devices such as smart phones, tablet computers and wearable gadgets.
The spread of high-definition video, with so-called 4K screens at the leading edge, is boosting demand for computing memory to store content.
"Small, high-capacity memories can of course be applied to smartphones, but they could also be used for wearable devices," the Toshiba spokeswoman said.
Manufacturers have traditionally competed with regular chips by trying to make the physical object smaller.
Toshiba, along with major rivals such as Samsung, believe they are reaching the physical limit, and are shifting toward 3D memories, where layering effectively a third dimension is used to boost the capacity of objects the same size.
Yasuo Naruke, Toshiba senior vice president, said in a statement: "Our determination to develop advanced technologies underlines our commitment to respond to continued demand (for) flash memory."
SanDisk president and chief executive Sanjay Mehrotra said the plant "will advance our leadership in memory technology into the 3D... era".
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