Alignment of the CMS Silicon Tracker

The CMS all-silicon tracker consists of 16\,588 modules with 25\,684 sensors in total. In 2010 it has been successfully aligned using tracks from cosmic rays and proton-proton collisions, following the time dependent movements of its innermost pixel layers. Ultimate local precision is now achieved by determining sensor curvatures, challenging the alignment procedure to determine about 200\,000 parameters. This is achieved in a global fit approach using {\scshape Millepede II} with the General Broken Lines track model. Remaining alignment uncertainties are dominated by systematic effects that bias track parameters by an amount relevant for physics analyses. These effects are controlled by including information about the $Z$~boson mass in the fit.