At the moment Micron currently owns approximately a third of Inotera so now it owns the lot.
Micron CEO Mark Durcan said that the deal was a compelling combination for both companies' shareholders and employees.
"The acquisition is the culmination of a highly successful seven year partnership with Inotera. It enables Micron to realize the full financial and operational benefit of Inotera's operations and provides a strong future for Inotera and its employees, who will become an even more critical part of Micron's success."
Micron buys all of Inotera's DRAM output and 35 per cent of Micron's total DRAM production. Inotera will be fully deployed on Micron's leading-edge 20nm technology by the middle of 2016.
Nanya owns a third of Inotera nd it is expected to back the sale.
Micron expects to finance the approximate US$4 billion for the remaining equity ownership interest in Inotera with approximately $2.5 billion of debt, up to $1 billion of Micron equity to Nanya and cash from Micron's balance sheet. Micron can terminate the transaction if it is unable to secure the US$2.5 billion of debt on satisfactory terms.
The companies expect the transaction to close in the middle of 2016.
Micron also announced the company has entered into a memorandum of understanding (MoU) to grant Nanya an option to license Micron 1x and 1y DRAM technologies. This new license agreement is in addition to Micron's existing license agreement for 20nm technology with Nanya.