Optical modulator and method of fabricating an optical modulator

A MOS capacitor-type optical modulator comprising:

• a silicon-on-insulator (SOI) substrate;
• a first doped region in a silicon device layer of the SOI substrate;
• and
• a second doped crystalline region laterally separated from the first doped region by a vertically extending insulator layer to form a lateral MOS capacitor region, wherein the first doped region, second doped crystalline region and insulator layer are formed from different materials,
• wherein the insulator layer extends at an oblique angle relative to the substrate, so as to laterally separate the second doped crystalline region from the first doped region.