The HL-LHC is due to start operation in the middle of 2026 with a center of mass energy of 14 TeV and a peak instantaneous luminosity up to 7x1034 cm-2s-1, to deliver 4000 fb-1 of integrated luminosity during 10 years of operation. The increased luminosity will result in seven times higher data rates and ten times higher radiation levels with respect to the LHC, posing stringent requirements on the design of the tracking detectors at the heart of the experiment. To maintain or even improve physics performance, and to cope with the new operational environment, the ATLAS experiment is preparing a complete replacement of the current inner detector. The new ATLAS Inner Tracker (ITk) will be an all-silicon detector, with pixel sensors close to the interaction point and strips sensors at larger radii, covering a surface of almost 200m2. The seminar will present the design of the ITk detector and its simulated performance, and discuss the semiconductor detector technologies developed to sustain 10 years of operation in the hostile environment at the HL-LHC.