This conference report presents searches for direct pair production of third generation squark performed with a dataset of proton-proton collision at {\sqrt s} = 13 TeV collected by the CMS experiment at the LHC, The data used correspond to an integrated luminosity of 2.3 fb^{-1}. No deviation from the standard model background is observed. The results are interpreted in the context of few simplified models. Within such models, stop masses up to 780 GeV and sbottom masses up to
890 GeV have been excluded at 95% CL for low mass neutralino.