Whereas the student takes one term to write a term paper and perhaps one year to write a master's thesis, the doctoral candidate may spend several years writing a doctoral thesis. These years must be highly productive and efficient in both research and writing; one must not procrastinate at all. The candidate who does not proceed efficiently may have difficulty completing the doctoral thesis before its statute of limitations runs out.
Writing a good doctoral thesis demands a lot of work from your side. As you are going to be a doctor, you are expected to be a master of the topic. And that in turns demands a lot of research and readings. You are expected to give some new outlook on the topic covered, which means you need to find something previously unexplored or not studied and even develop theories on the topic. The following outlines the main areas to be worked on to complete a good doctoral thesis:
How I wrote a PhD thesis in 3 months - James Hayton PhD