I am a beginner with respect to MOSFETs and have just begun studying them at college 2 weeks back. What I am actually struggling with is the basic functional differences between MOSFETs and JFETs. Two of them are- dielectric and substrate, both of which are there in MOSFETs. However, I don't understand much, the significance of having a dielectric, when I thought the direct application of a gate bias could have helped, though with opposite polarity. Moreover, I don't understand why the term "junction" is used to describe the interface between Gate and Drain/Source? And why do books talk about reverse/forward biasing these "junctions" when we know they are nothing but tiny overlaps of Gate over Drain/Source? Do these tiny overlaps play such important role in MOSFET functioning or does it have something to do with the Substrate-Drain/Source junctions? And, can't a substrate bias alone work without gate bias, as in the case of JFETs, where we have only one single voltage(gate) controlling the channel as input terminal? Does a gate bias also control the substrate polarity, as the substrate bias does, but on the opposite face of the substrate? These are a few initial doubts that I wanted to share. They might appear really stupid, but for me I know they're vital. If not cleared, they could snowball into a big trouble for me in the future. So kindly reply... Thankyou! PS.: This is not a homework question. Please don't mistake it for one!