Method and apparatus for fabricating semiconductor device with photodiode

Abstract

On a surface of a silicon substrate, N.sup.+ type buried layer and N-type epitaxial layer are formed in order, and an isolation layer reaching the silicon substrate from the surface of the N-type epitaxial layer is formed to define a photodiode. In the surface of the photodiode, a rectangular recess is selectively formed toward inside of the N-type epitaxial layer. On the side face of the recess, a silicon oxide layer is formed. In the region surrounded by the silicon oxide layer, a photo absorbing layer and so forth is formed. On the other hand, in an optical waveguide, a LOCOS oxide layer is formed toward inside from the surface of the N-type epitaxial layer. The N-type epitaxial layer is sandwiched between the LOCOS oxide layer and the N.sup.+ type buried layer. The refraction indexes of the LOCOS oxide layer and the N.sup.+ type buried layer are smaller than that of the N-type epitaxial layer. Thus, the N-type epitaxial layer serves as an optical passage to efficiently introduce a light beam into the photo absorbing layer of the photodiode.