Question

Question 1 (25 marks) Here below (Fig. 1) is the cross-sectional structure of an integrated circuit (IC) showing a metal- oxide-semiconductor field effect transistor (MOSFET). The four terminals of the MOSFET are connected to four voltages V1, V2, V3, and V4 respectively V V2 V: SO n+ n+ p-type Fig. 1 (a). What channel type is the MOSFET shown? (1 mark) (b). What are the common names of the four terminals connected to V1, V2, V3, and V4 respectively? Note that the terminal with V2 is usually connected to ground while the terminal with V4 is usually connected to a positive voltage. (5 marks) (C). A channel is formed in the MOSFET when V3 > 1.0 V and V1 = 0 V while the other two terminals are open-circuited. If Vi = V2 = 0 V and V4 varies from 0 V to 3.0 V, sketch a graph with 142 (current flowing through the channel) versus V4 for V3 = 1.2 V, 1.4 V and 1.6 V. Any turning point(s) or important features (e.g. relative current levels) must be shown clearly or labelled explicitly. (9 marks) (d). Draw the physical layout of the MOSFET according to the cross-sectional structure shown above. The layout should occupies a minimal chip area corresponding to the structure shown. Make sure that all the IC layers are clearly labelled and the lambda design rules are followed approximately (10 marks)

Answer 1

A] What channel type:

P- Channel MOSFET:

The P- Channel MOSFET has a P- Channel region between source and drain. It is a four terminal device such as gate, drain, source, body. The drain and source are heavily doped p+ region and the body or substrate is n-type. The flow of current is positively charged holes. When we apply the negative gate voltage, the electrons present under the oxide layer with are pushed downward into the substrate with a repulsive force. The depletion region populated by the bound positive charges which are associated with the donor atoms. The negative gate voltage also attracts holes from p+ source and drain region into the channel region.

B] Common thermal