This paper reports on a novel, simple yet reliable, unbalanced SOI Mach-Zehnder (M-Z) interferometer architecture based on 1.2 μm CMOS process and adapted post-processing for the waveguide sidewalls. The fabricated electro-optical device is based on multiple PIN diode bars integrated on top of a SOI silicon waveguide and can be operated either at: (I) high-frequency (few MHz) based on the plasma dispersion effect and (II) low frequency (<1 MHz) based on the thermo-optic effect. The device main characteristics and figures of merit are presented and discussed.