Silicon is the most diffused material for microelectronic industry and, in recent times, it is becoming more and more widespread in integrated optic and optoelectronic fields. Nowadays it is possible to realize in silicon, using the traditional microelectronic techniques, a huge variety of passive and active devices, like waveguide, switch, modulators, whose operation range is in the second and third optical telecommunication windows. In this poster we propose a simulation of an integrated waveguide-vanishing-based modulator realized by ion implantation in SOI wafer. The active region is 3x3 micron wide and the lateral confinement is guaranteed by two highly-doped As (8×10+19 cm-3) and B (2×1019 cm-3) implanted regions with a depth of one micron. This type of structure allows to obtain a planar device; thus an easier integration with electronic devices is possible to obtain. The implantation process has been carefully tuned in order to get high doping uniformity and sharp profile. The resulting channel waveguide shows single mode operation and propagation loss of about 1.8 dB/mm. The modulation is based on a lateral p-i-n diode, that allows to inject free carriers into the rib volume between the doped regions. The resulting optical behavior is the vanishing of the confinement in the rib region and consequently the cut-off of the supported mode. This phenomenon occurs at driving voltage of about 1.0 V, with electrical power consumption of 2 mW, and implies a rapid propagating characteristics variation, with following optical beam lateral redistribution into the structure. Both fabrication process and operation (electrical and optical) simulations have been carried out. Results show that an optical modulation depth close to 100% can be reached with a rise time of about 10 ns. Fall time can be even faster, if a proper reverse polarization is applied to the device.