6.7 Physical Structures of MOSFET

• The on-resistance of MOSFET depends on its physical properties (ie. geometry)
• Silicon doped with material rich in electrons is called n-type semiconductor (n+) 
• Silicon doped with material rich in holes is called p-type semiconductor (p+)

 

• Ron is the resistance of n channel
• Rn is resistance per square of n channel MOSFET in on state.
• Ron = (Rn*L)/W
• In VLSI technology, there is min fabricatable value for MOSFET channel length