A novel low-loss 50-Ω coplanar waveguide with V-groove on an SOI substrate is proposed.Through a CMOS-compatible process and anisotropic etching of silicon, surface silicon is removed from the SOI.The measured results show that the V-groove coplanar waveguide causes about 50% less loss than the conventional one at a high frequency of up to 40 GHz. A novel low-loss 50-Ω coplanar waveguide with V-groove on an SOI substrate is proposed. Through a CMOS-compatible process and anisotropic etching of silicon, surface silicon is removed from the SOI. The measured results show that the V-groove coplanar waveguide causes about 50% less loss than the conventional one at a high frequency of up to 40 GHz.