Which type of virus causes, the baby to die inside the womb?

Parvovirus. Parvovirus b19 kills unborn children by causing destruction of the precursor cells that produce red blood cells. The child becomes edematous ("hydrops") and dies. Sometimes transfusing the child in the womb can safe their life.
Not usually a virus. The most common infectious reasons for stillbirth are not viruses. Highest on the list is probably syphilis, an std that is definitely still around. Also listeria and toxoplasma. Rubella and herpes are viruses and can also cause fetal death. Talk to your OB about how to reduce your risk of exposure to these diseases.