A substrate comprising a first transistor element and a second transistor element is provided. A layer of a material is deposited over the first transistor element and the second transistor element. A portion of the layer of material is modified, which may be done, e.g., by irradiating the portion with ions or performing an isotropic etching process to reduce its thickness. An etching process adapted to remove the modified portion of the layer of material more quickly than an unmodified portion of the layer located over the second transistor element is performed.