Due to integrated circuit performances increase, insulator materials with dielectric constant lower than 2.4 are requested for microelectronic interconnections. Mesoporous methylsilsesquioxane (MSQ) thin films are promising candidates for this application. However, previous studies reported low mechanical properties for these materials. These properties were usually modelized using cellular solids mechanic without taking into account chemical structure. In this work, a physical model is proposed which allows predicting elastic properties with respect to the matrix crosslinking. Several ways were used to obtain MSQ layers with different porosities and matrix crosslinking. Impact of elaboration process and curing on crosslinking were investigated using FTIR analysis and spectroscopic ellipsometry. Elastic properties were determined by nanoindentation. A correlation between elastic properties and FTIR Si-O-Si contribution is observed for all the studied samples. (c) 2005 Elsevier B.V. All rights reserved.