NEW YORK (Thomson Financial) - Shares of Tessera Technologies Inc. plummeted Tuesday after the U.S. Patent Office rejected Tessera's patent in reexamination case brought by Siliconware.

Siliconware sought reexamination of five heavily-licensed Tessera patents that are part of Tessera's compliant chip license, a portfolio that has been previously asserted in numerous litigations and has generated more than $250 million dollars in licensing profits, according to Tessera.

The patent is one of four for which Tessera is seeking remedy for infringement. All the patents are broadly licensed to companies in the semiconductor industry including DRAM manufacturers Samsung, Hynix, Qimonda (nyse: QI - news - people ) and Micron, according to a Tessera press release from Dec. 10, 2007.

On Feb. 29, the Patent Office rejected every claim of the patent in reexamination.

Since Feb. 15, the Patent Office rejected claims being asserted by Tessera against several chip manufacturers in U.S. district court lawsuits, International Trade Commission actions and arbitration proceedings, according to a press release issued by Orrick, Herrington and Sutcliffe LLP, a global law firm that represented Siliconware with national firm, Novak Druce + Quigg LLP.

'On Feb. 26, the International Trade Commission took the rarely-employed step of staying a hearing based on Siliconware's reexaminations. The ITC stayed Tessera's investigation against Spansion (nasdaq: SPSN - news - people ), Qualcomm (nasdaq: QCOM - news - people ), ATI Technologies, Motorola (nyse: MOT - news - people ), STMicroelectronics (nyse: STM - news - people ) and Freescale,' the press release said.

Trading of Tessera stock was halted midday for news pending after it fell as much as 52% to a new all-time low of $11.11. Prior to the halt, 17.7 million shares changed hands, or more than 12 times the full-day average over the past 30 days of about 1.4 million shares.