The justices refused to hear the Federal Trade Commission's plea to reinstate the commission's ruling that Rambus, based in Los Altos, Calif., violated antitrust law.

Separately Monday, the U.S. District Court for the Northern District of California granted the company supplemental damages on patent infringements by Hynix Semiconductor, driving Rambus' shares up 30 percent in after-hours electronic trading.

Back in 2002, the FTC accused Rambus of not disclosing that it held or was seeking patents on technologies that were incorporated into industry engineering standards for dynamic random access memory, or DRAM, chips.

Rambus had participated in the setting of those standards in the 1990's. DRAM chips are the most common type of memory chips used in personal computers.

The FTC capped royalties the company could collect and required that it license the technology.

Last April, a federal appeals court ruled that the FTC had not provided enough evidence to prove that Rambus attempted to establish a monopoly on these memory chips. The Supreme Court refused to review the appellate case.

The Bush administration had declined to back the FTC in its appeal to the high court.

"After enduring years of lost business, uncertainty, and spending millions of dollars defending ourselves against the FTC's ill-founded allegations, we're pleased the Supreme Court has put an end to these claims," said Tom Lavelle, Rambus's general counsel.

In the separate California decision, Hynix must pay Rambus royalties of 1 percent and 4.25 percent on two devices made or sold in the U.S. starting in 2006.

The court did deny Rambus' request that Hynix be barred from selling the chip technology, and instead ordered the two companies to negotiate a license to let Hynix continue to sell its products.

The case with Hynix was originally filed by Hynix against Rambus in August 2000.

Shares of Rambus closed up 6.2 percent, or 39 cents, to $6.70. The stock surged another 30 percent to $8.75 in after-hours trading.

A service of YellowBrix, Inc.