Metasurface based microlenses (or metalenses) are planar microlenses which could be an alternative to replace refractive microlenses made of resist on image sensor. This paper aims at exploring through simulation the integration of metalenses on CMOS pixel array. Theses simulations precede metalenses implementation on STMicroelectronics 2.8, 4 and 8 μm pixels with updated fabrication process involving immersion photolithography. Emphasis is given on improving metalenses performances with consideration to fabrication capacities available.