Photonics device and CMOS device having a common gate

A method for forming a photonics device and a CMOS device with a common gate comprising:

• defining a photonics device portion and a CMOS device portion on a semiconductor chip where a photonics device and a CMOS device, respectively, are to be fabricated;
• forming a metal or polysilicon gate material on the CMOS device portion;
• depositing germanium on the photonics device portion and on the metal or polysilicon gate material on the CMOS device portion;
• planarizing the germanium to form a coplanar layer of germanium and metal or polysilicon gate material;
• etching the germanium to define a gate on the photonics portion and a gate extension that extends towards the CMOS device portion;
• etching the metal or polysilicon gate material to define a gate on the CMOS device portion and a gate extension that extends toward the photonics device portion and joins the gate extension from the germanium gate portion wherein the respective joined gate extensions form a common gate between the photonics device portion and CMOS device portion;
• forming spacers on the germanium gate and metal or polysilicon gate;
• encapsulating the germanium gate with a nitride;
• and
• heating the photonics device portion to cause melting and crystallization of the germanium gate.