High-resistivity silicon (with resistivity above 1,000 Ω·cm) holds an irreplaceable position in RF MEMS devices. Thanks to its ultra-low net doping concentration (below \(10^{12}\ \mathrm{cm^{-3}}\)), it delivers extremely low RF substrate loss. Coplanar waveguides fabricated on high-resistivity silicon achieve an insertion loss of less than 2 dB/cm within the frequency band up to 26 GHz, whereas low-resistivity silicon substrates cannot be directly adopted due to excessive microwave loss. Accordingly, high-resistivity silicon substrates are widely applied in RF front-ends, microwave transmission lines, digital phase shifters, terahertz devices and other related fields.

Nevertheless, low-resistivity silicon (typically with resistivity ranging from 0.001 to 1 Ω·cm) possesses distinctive application merits. Characterized by high doping concentration and excellent electrical conductivity, alongside low manufacturing cost and mature process flow, low-resistivity silicon is ideal for mass-produced logic chips, memory devices, solar cells and similar products.

Cutting-edge research on high-resistivity silicon has emerged continuously in recent years. In 2026, researchers successfully developed a novel monolithic device integrating waveguides and MEMS structures on a single high-resistivity monocrystalline silicon substrate. The device features ultra-low power consumption of 3.6 mW and superior switching performance with an extinction ratio of 13.69 dB, which is expected to facilitate the miniaturization and low-power design of photonic integrated circuits for 6G communications. This demonstrates that precise regulation of silicon substrate resistivity has become a pivotal technology driving the advancement of next-generation communication technologies.