Thanatophobia :

 Thanatophobia is the fear of death or fear of the death process. It is a deeper form of the classic fear of death that affects more or less everyone. 
The word thanatophobia comes from two ancient Greek words:
“thanatos-” wich means “death” or is the name of the Greek God of death, and “phobos” wich means “fear”.
Thanatophobia is different from the necrophobia which is the fear of dying people. The causes of this fear are very unknown, it is assumed that this is an extreme development of fear of “regular” death. 
Forms of thanatophobia can manifest themselves by organ donation or by visiting patients in hospitals. 

Sources:

• Heath-Line
  
• Wikipédia