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In this paper, the impact of substrate resistivity on the functional passive components of radio frequency (RF) complementary metal-oxide-semiconductor circuits for system-on-a-chip applications is investigated. This paper carefully extracted the dielectric constant and loss tangent of the silicon substrate with different substrate resistivities by using the aluminum coplanar waveguide. The different dielectric relaxation (cutoff) frequencies as a function of silicon substrate resistivity are compared under different requirements for substrate noise isolation, RF passive device design, and 3-dB-level RF passive device design. It is found that the new dielectric relaxation frequencies of the silicon substrate, which can be used for the implementation of 3-dB-level RF passive device design, are much higher than for the substrate noise isolation. Finally, the integrated millimeter-wave filter example, a low-pass filter with a filter cutoff frequency of fc = 31 GHz, was designed and evaluated directly on the silicon substrates with different resistivities. Experimental results of the fabricated filter showed good agreement with the simulated results and designed concept.