The pixel detector for the CMS phase-II upgrade

The high luminosity phase of the Large Hadron Collider (HL-LHC) requires a major pixel detector R\&D effort to develop both readout chip and sensor that are capable to withstand unprecedented extremely high radiation. The target integrated luminosity of 3000~fb$^{-1}$, that the HL-LHC is expected to deliver over about 10 years of operation, translates into a hadron fluence of $2\times10^{16}$~1MeV~eq.n.~/~cm$^2$, or equivalently 10~MGy of radiation dose in silicon, at about 3~cm from the interaction region where the first layer of the pixel detector could be located. The CMS collaboration has undertaken two baseline sensor R\&D programs on thin n-on-p planar and 3D silicon sensor technologies. Together with the ATLAS collaboration it has also been established a common R\&D effort for the development of the readout chip in the 65~nm CMOS technology. Status, progresses, and prospects of the CMS R\&D effort are presented and discussed in this article.