Semiconductor device and manufacturing method thereof

A semiconductor device comprising:

• a first insulating layer;
• an optical waveguide formed on the first insulating layer and having a first side surface and a second side surface which are located opposite sides with each other;
• a first slab portion formed on the first insulating layer such that the first slab portion is adjacent to the first side surface;
• a second insulating layer formed on the optical waveguide;
• and
• a conductive layer formed on the second insulating layer,
• wherein the optical waveguide has a first conductivity type,
• wherein the first slab portion comprises;
• a first portion having a second conductivity type opposite to the first conductivity type;
• a second portion located farther from the optical waveguide than the first portion and having the first conductivity type;
• and
• a third portion formed between the optical waveguide and the second portion and having the first conductivity type,
• wherein the semiconductor device further comprises:
• an interlayer insulating layer formed on the first insulating layer such that the interlayer insulating layer covers the optical waveguide, the first slab portion, the second insulating layer, and the conductive layer;
• a first via formed in the interlayer insulating layer such that the first via reaches the conductive layer;
• a second via formed in the interlayer insulating layer such that the second via reaches the first portion;
• and
• a third via formed in the interlayer insulating layer such that the third via reaches the second portion.