A semiconductor integrated circuit that reduces a loss in an electrical signal and a method for manufacturing the semiconductor integrated circuit are provided. The semiconductor integrated circuit comprises a first region on which an optical circuit is to be formed and a second region on which an electrical signal wiring is to be formed. The first region comprises an Si substrate (502), a BOX layer (504) formed on the Si substrate (502), a first SOI layer (506) formed as an optical circuit on the BOX layer (504), and a first SiO2 layer (508) formed on the first SOI layer (506). The second region comprises the Si substrate (502), the BOX layer (504), a second SiO2 layer (508) formed on the BOX layer (504), and an electrical signal wiring (510) formed on the second SiO2 layer (508).