She could not comment on how much capacity has been shifted to other plants.
By mid-May, the company aims to deliver a timetable for when chip production at both the plant's 200-millimeter and 300-millimeter wafer lines at Naka will return to pre-quake levels.
"The company is working in earnest with more than 2,000 additional support workers dispatched from outside Renesas Electronics companies to help speed up the resumption of production as much as possible," the company said.
More than 100 microcontrollers, or MCUs, can go into a modern vehicle, and Renesas controls about 41 percent of the global market -- with 90 percent of its global capacity based in Japan.
Renesas' Naka plant in northeastern Japan accounts for about 25 percent of its global automotive MCU capacity. It has been offline since the March 11 earthquake.
Naka has two wafer lines. One makes 200-millimeter wafers that are then cut into individual microcontroller chips, some of which end up in cars. The other makes 300-millimeter wafers, divided into so-called system-on chips used mostly in digital cameras and mobile phones.
The 200-millimeter chips are essential to everything from electronic parking brakes, pre-crash seat belts and engine control units to onboard entertainment systems, stability control and power steering.
Damage to plants in Japan has emerged as a key pinch point for global automakers. Tier 1 suppliers that rely on such chips as a sub-component can't supply carmakers without them.
Renesas' rival, Freescale Semiconductor Inc., the world's second-biggest maker of automotive computer chips, has decided to permanently close its only plant in Japan due to earthquake damage and is racing to add capacity at other factories.
The Austin, Texas-based chipmaker had announced in 2009 it would shut down the factory by December this year. But after assessing damage, Freescale decided it wasn't worth repairing.