Semiconductor device and method of manufacturing thereof

A semiconductor device, comprising:

• a field effect transistor disposed over a first main surface of a semiconductor substrate, wherein the field effect transistor includes a gate structure and a source/drain region;
• a plurality of alternating first layers having a first refractive index and second layers having a second refractive index over an opposing second main surface of the semiconductor substrate, wherein the first refractive index and the second refractive index are different;
• and
• a conductive via disposed in the plurality of alternating first layers and second layers, wherein the conductive via passes through the semiconductor substrate and is in direct electrical contact with the source/drain region.

A semiconductor device, comprising:

• a field effect transistor disposed over a first main surface of a semiconductor substrate, wherein the field effect transistor includes a gate structure and a source/drain region;
• a plurality of alternating amorphous silicon layers and silicon oxide layers over an opposing second main surface of the semiconductor substrate;
• a conductive via disposed in the alternating amorphous silicon layers and silicon oxide layers, wherein the conductive via passes through the semiconductor substrate and is in electrical contact with the source/drain region;
• and
• a metal silicide between the source/drain region and the conductive via.