I will present a study on the formation of early-type galaxies (ETGs) through mergers with a sample of 70 high-resolution numerical simulations of binary mergers of disc galaxies (with 10 per cent of gas) and 16 simulations of ETG remergers. These simulations, designed to accompany observations and models conducted within the Atlas3D project, encompass various mass ratios (from 1:1 to 6:1), initial conditions and orbital parameters. I will show that binary mergers can either produce fast rotating galaxies (at all mass ratios) and slow rotating galaxies (for mass ratios of 1:1 and 2:1). Most Slow Rotators formed in these binary disc mergers hold a stellar Kinematically Distinct Core (KDC) in their ∼ 1-3 central kilo-parsec : these KDCs are built from the stellar components of the progenitors. The mass ratio of the progenitors is a fundamental parameter for the formation of Slow Rotators in these binary mergers, but it also requires a retrograde spin for the galaxies with respect to the orbital angular momentum. By looking at the kinematics of the remnants of major mergers of spiral galaxies in the GalMer database, I can confirm the importance of the spin of the progenitors in the formation of the fast and slow rotating galaxies.