Questions about layout of transistors

[Ahmed Atiya]

Hi all,

I want to ask 2 question about layout of transistors

1- which is preferable in layout of transistor to increase number of fingers or to make multiplier from the transistor.

2- why there is a pplus layer in the PMOS and nplus in NMOS

thanks for your help

 

[road_0506]

Re: layout questions

1- which is preferable in layout of transistor to increase number of fingers or to make multiplier from the transistor.
---- in my own opinion, they are the same.

2- why there is a pplus layer in the PMOS and nplus in NMOS
--- the P+ and the N+ are put in the active to make it P and N type, respectively.

 

[anujoamon]

Re: layout questions

fingering and mpar are most of times considered same by the layout design engineer.

but i got a description from one design engineer which says fingering is like folding a transistor while multiplying factor makes a bus .

Assume two transistors connected in series and have a finger of two. so the common net will be common for all four transistors, while in case of multiplying factor, there will be two pair os devices which will be connected in parallel... valid only when both devices are pmos or nmos.

hope the image attached clarifies it further

 

[erikl]

Re: layout questions

2- why there is a pplus layer in the PMOS and nplus in NMOS

To achieve a low-resistive contact for the MOSFET's bulk connection.