Coplanar wave-guide grounded lines (CPWGs) with micro-machined via-holes have been designed, realised on high-resistivity silicon wafers, and tested up to 40 GHz. Several configurations, designed by changing the dimensions of the micro-machined via-holes used for the ground connection, as well as their number and separation, have been compared to get the best electrical matching conditions. Wide-band matching and suppression of bulk resonance peaks have been obtained within the 40 GHz range.