German chipmaker Infineon Technologies and several of its peers could be penalised by EU antitrust regulators.
The European Commission said in a statement it had sent objections setting out its concerns to the companies involved, without identifying them.
They would face fines up to 10 per cent of their global revenue if found guilty.
The EU competition authority said it sent the charge sheet to the companies after talks to settle the case, which would have included a 10 per cent cut in fines, broke down.
Infineon confirmed receiving the statement of objections.
The Commission said it issued the charge sheet after talks to settle the case including a 10 per cent reduction in fines, broke down.
NXP Semiconductors and France-based STMicroelectronics, both of which had previously said they were under investigation, said they had not received the EU document.
Gemalto, the world's largest maker of smart cards, said it was not a target of the investigation.
Atmel previously said it was cooperating with the investigation, while Renesas Technology - a joint venture between Hitachi and Mitsubishi Electric - has confirmed the regulatory raids.
The case started in January 2009 with raids on companies in several EU countries.
The firms can ask for a closed-door hearing to defend themselves before EU antitrust officials and national competition regulators.