I have a pretty fundamental question related MOSFET devices. I am confused about whether the terms body, bulk and substrate are all just names for the same thing or are there actually some differences between what each is referring to ? I feel like I have heard them all being used interchangeably to describe the same thing.
They are the same. And if the FET is deposited within a special implant, that implant called the tub or the well, then the tub and the well have become the same as body or bulk, and the substrate remains the larger structure upon which all the FETs of either polarity (some in wells for that reversed polarity) are implanted, as well as resistors and capacitors and diodes. And the bond-pads. And the special smiley-faces some layout people add.