Infineon has agreed to buy Cypress Semiconductors in a deal valuing the U.S. chipmaker at 9 billion euros ($10.06 billion), including debt, the German company said on Monday.

The cash offer of $23.85 per share represents a 46% premium to Cypress' share price over the last month, Infineon said.

Infineon is targeting cost synergies of 180 million euros per year by 2022 and revenue synergies of more than 1.5 billion euros in the long term. The Germany chipmaker added that it intends to finance about 30% of total transaction value with equity and remainder with debt as well as cash on hand.

Infineon's share price fell 6.5% Monday to the bottom of the Stoxx 600 as investors reacted to the deal. But Infineon Chief Financial Officer Sven Schneider told CNBC's "Street Signs Europe" Monday that the cost and revenue synergies meant the "transaction makes a lot of sense."

Cypress shares soared 27% in pre-market trade, meanwhile.