Intel will increase the size of the assembly and test facility it is building in Vietnam from 150,000 square feet to 500,000 square feet and raise its investment from the $300 million announced in February to $1 billion, the company announced today. The build-out will result in the largest single factory within Intel’s assembly and test network.

When completed, the Vietnam facility will be the seventh assembly and test site in Intel’s network, which only include international sites in Penang and Kulim, Malaysia ; Cavite, Philippines ; Chengdu and Shanghai, China ; and San Jose, Costa Rica. The Vietnam facility will go online in 2009 and will employ about 4000 people, Intel said.