Japanese semiconductor company Renesas Electronics is in talks to acquire U.S. chipmaker Maxim Integrated, according to several sources close to the matter, in what could be close to a $20 billion acquisition.

A deal isn't imminent and one may not happen, said those people, who asked not to be named because the discussions are private. Renesas has a market capitalization of about $20 billion, while Maxim is valued at more than $16 billion.

Reached by CNBC, Renesas denied "speculations" that it is "in talks for a possible acquisition."

"Certain media reports were published today that Renesas is in talks for a possible acquisition," a Renesas spokeswoman told CNBC. "They were not based on a Renesas announcement. The company denies the speculations in the reports."

Renesas said it has no further comment. A spokeswoman for Maxim declined to comment.

Shares of Maxim, which jumped about 12 percent in during Monday's trading session, gave back much of those gains following reports that Renesas denied it was in talks.