  The physics aims at the proposed future high-energy linear $e^+e^-$ collider
CLIC pose challenging demands on the performance of the detector system. In
particular, the vertex and tracking detectors have to combine a spatial
resolution of a few micrometres and a low material budget with a time-stamping
accuracy of a few nanoseconds. For the vertex detector, fine-pitch sensors,
dedicated 65nm readout ASICs, fine-pitch bonding techniques using solder bumps
or anisotropic conductive films as well as monolithic devices based on
Silicon-On-Insulator technology are explored. Fully monolithic CMOS sensors
with large and small collection electrodes are under investigation for the
large surface CLIC tracker. This contribution gives an overview of the CLIC
vertex and tracking detector R&D, focusing on recent results from test-beam
campaigns and simulation-based sensor optimisation studies.
