We report a compact 2×2 Mach–Zehnder interferometer (MZI) electro-optic switch fabricated on a silicon-on-insulator using standard complementary metal-oxide semiconductor (CMOS) processes. With a short modulation arm length of 200 μm, the crosstalk is reduced to 22 dB by the new modulation scheme of push–pull modulation with a pre-biased π/2 phase shift. The new modulation scheme can also work with a fast switching time of about 5.4 ns.