Silicon consumption in a selective tungsten chemical vapor deposition (SWCVD) process using SiH4 reduction of WF6 was investigated. In the SWCVD process, the Si surface was consumed through the reduction of the WF6 until a continuous W cladding layer was formed. The dependence of Si consumption on growth temperature and impurity concentration was investigated by measuring the decrease in silicon on insulator (SOI) thickness using an ellipsometer. The consumption decreased with a decrease of the growth temperature dependent on an activation energy of 0.104 eV; the consumption increased in proportion to the phosphorus concentration, in the region where the concentration was above about 9 x 10(19)cm(-3). It was demonstrated that SWCVD could be applied to fabricate a W cladding layer on the gate/source/drain regions of the fully depleted 20 nm SOI complementary metal oxide semiconductor field effect transistors (CMOSFETs). Moreover, optimizing the fabrication process to avoid excess impurity concentration in the n(+)-S/D regions of the n-MOSFETs will make this technology suitable for use with thinner SOI devices.