We report an experimental study of the defects induced by a TIN metal gate. Nitrogen-induced defects due to diffusion from the nitrided gate have been evidenced. The energy profile of the density of interface states in the silicon band gap has been extracted by original spectroscopic charge pumping measurements. We have identified two specific peaks near the Si band edges as the signature of N diffusion. The density of defects has then been correlated to the electron mobility degradation and compared to a theoretical model which well reproduces the experimental data. (C) 2011 Elsevier Ltd. All rights reserved.