Upgrade of the CMS tracker

The LHC machine is planning an upgrade program which will smoothly bring the luminosity up to or above $5\times 10^{34}$ cm$^{-2}$s$^{-1}$ sometimes after 2020, to eventually reach an integrated luminosity of 3000 fb$^{-1}$ at the end of that decade. The foreseen increases of both the instantaneous and the integrated luminosity by the LHC during the next ten years will necessitate a stepwise upgrade of the CMS tracking detector. During the extended end-of-year shutdown 2016-2017 the pixel detector will be exchanged with a new one. The so-called Phase1 Pixel foresees one additional barrel layer and one additional end-cap disk, a new readout chip, reduction of material, and the installation of more efficient cooling and powering systems. In the so-called Phase2, when LHC will reach the High Luminosity (HL-LHC) phase, CMS will need a completely new Tracker detector, in order to fully exploit the high-demanding operating conditions and the delivered luminosity. The new Tracker should have also trigger capabilities. To achieve such goals, R\&D activities are ongoing to explore options and develop solutions that would allow including tracking information at Level-1. The design choices for the CMS pixel and outer tracker upgrades are discussed along with some highlights of the R\&D activities.