Lockyer said that the joint suit, to be filed on Friday in the District Court of Northern California, will charge the companies with "a four-year conspiracy to fix DRAM chip prices, artificially restrain supply."
He identified the companies as Infineon Technologies AG; Hynix Semiconductor, Inc.; Micron Technology, Inc.; Mosel Vitelic, Inc.; Nanya Technology Corp.; Elpida Memory, Inc., and NEC Electronics America, Inc.
Infineon, Hynix, and Micron, together with Samsung - which is not named in the suit - reportedly control roughly 70 percent of the US computer chip market, worth $5 billion in 2003.
The price-fixing allegedly took place from 1998 through June 2002.
"Price fixing strikes at the heart of free competition and fair play which underpin our economic system and protect the interests of businesses and consumers alike," Lockyer said in a statement.
"The defendants in this case conspired to rig the US market for this essential computer product, working together to keep prices artificially high."
The price rigging cost US chip customers hundreds of millions of dollars and hit California particularly hard because it is home to Silicon Valley companies, according to Lockyer.
The lawsuit stemmed from an antitrust case the US Department of Justice launched in 2002 against what it branded "one of the largest cartels ever discovered," according to Lockyer.
US-based Micron reportedly cooperated with investigators in exchange for immunity from criminal charges.
The federal case resulted in Samsung, Hynix, Infineon, Elpida, and a dozen individuals pleading guilty to price-fixing and paying fines totaling more than $730 million.
Korean chipmakers Samsung Electronics Company Ltd. and Hynix made plea deals with prosecutors last year, agreeing to pay $300 million and $185 million respectively in fines.
German chipmaker Infineon pleaded guilty in 2004 and was fined $160 million for its part in the conspiracy, prosecutors said.
It was not immediately clear why Samsung was not included as one of the targets in the joint lawsuit.
The "widespread antitrust conspiracy" illegally enriched the accused chipmakers at the expense of US computer customers, the states' lawsuit charged.
The defendants started discussing and coordinating the prices that they charged to large computer manufacturers in 1998 when the DRAM market had excess supply, according to the complaint.
Computer-makers affected by the price-fixing included Apple Computer, Dell Inc., Hewlett-Packard Company, Compaq Computer Corporation, Gateway Inc., and International Business Machines, prosecutors said.
In 2001 the defendants "agreed to reduce supply in order to artificially raise prices," the legal complaint charged.
DRAMs are the most common semiconductor memory product, providing high-speed storage and retrieval of electronic information for computer, telecommunication, and consumer electronic products.
They are used in personal computers, laptops, servers, printers, hard disk drives, personal digital assistants, modems, mobile phones, digital cameras, video recorders and TVs, game consoles, and digital music players.
© 2006 Agence France-Presse
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