The cunning plan is to lower production costs amid intensifying price competition in the smartphone market.

If Samsung can get its display unit costs down, it might steal a march on its rivals by offering a better quality at a lower price. At the moment, everyone and his dog can do low quality and cheap. Samsung's rival Apple does medium quality and expensive.

The investment by Samsung Display comes on top of a $1 billion it has earmarked for a new OLED display module assembly plant in Bac Ninh province, which began production in the first quarter.

The fresh $3 billion in spending will be spread out over several years until 2020.

Samsung Display's annual capital spending has averaged $3.4 billion in the past three years.

Samsung Electronics, the world's top smartphone maker, in November applied for approval to invest $3 billion in building a second smartphone factory in northern Vietnam.