Hello

There are two programs one is Integrated M.Sc.- PhD

Another one is only PhD. To enter in integrated msc PhD you have to qualify IIT JAM with a good rank approximately less than 400 and then qualify in interviews conducted by the Institute. Institute which provide integrated M.Sc- PhD are all the IISERs ,IISc Bangalore, TIFR and some IITs.

And after you have completed M.Sc. if you have qualified CSIR NET then you can apply for PhD in different universities and if you have good rank in gate then you can apply in IITs and IISERs.

Hope this helps.