what is MOS layers and symbolic diagram transition to MASK form
Answers
Answer:
The most basic element in the design of a large scale integrated circuit is the transistor. For the processes we will discuss, the type of transistor available is the Metal-Oxide-Semiconductor Field Effect Transistor (MOSFET). These transistors are formed as a ``sandwich'' consisting of a semiconductor layer, usually a slice, or wafer, from a single crystal of silicon; a layer of silicon dioxide (the oxide) and a layer of metal. These layers are patterned in a manner which permits transistors to be formed in the semiconductor material (the ``substrate''); a diagram showing a typical (idealized) MOSFET is shown in Figure gif. Silicon dioxide is a very good insulator, so a very thin layer, typically only a few hundred molecules thick, is required. Actually, the transistors which we will use do not use metal for their gate regions, but instead use polycrystalline silicon (poly). Polysilicon gate FET's have replaced virtually all of the older devices using metal gates in large scale integrated circuits. (Both metal and polysilicon FET's are sometimes referred to as IGFET's --- insulated gate field effect transistors, since the silicon dioxide under the gate is an insulator. We will still continue to use the term MOSFET to refer to polysilicon gate FET's.)