Munich based Infineon has 32,000 employees

The three Germans and an American will each pay a fine of $250,000 (�129,000) and serve a prison term of up to six months.

Infineon agreed in September to pay a fine of $160m after pleading guilty to one count of price-fixing.

US prosecutors said their investigation into memory chip prices will continue.

The four sales executives were named as Heinrich Florian, Guenter Hefner, Peter Schaefer and Rudd Corwen.

These four executives are the first to plead guilty to a charge of fixing prices in what is still a very active and far-reaching investigation US Justice Department

They pleaded guilty in an agreement filed in a San Francisco federal district court.

The Justice Department is investigating complaints about price fixing of dynamic random access memory (dram) memory chips.

These are the most common type of semiconductors, widely used in consumer products like mobile phones and PCs.

"These four executives are the first to plead guilty to a charge of fixing prices in what is still a very active and far-reaching investigation into anti-trust violations in the dram industry," said the Justice Department's anti-trust division's head of criminal enforcement Scott Hammond.

"This case reinforces our commitment to investigate and hold accountable all conspirators, whether domestic or foreign, that harm American consumers through their collusion," said Hewitt Pate, assistant attorney general in the anti-trust division.

Infineon, whose US operation is based in San Jose, California, has more than 32,000 employees and recorded sales worth 6.15bn euros in 2003.

Two of the four executives have left the firm and two have been moved to non-sales jobs, Reuters cited an Infineon company spokesman as saying.