The advantages of Snake-Shape MOS Transistor

[abonic]

Dear all,
Recently, I've found a type of MOS Transistor characterized by snake-shape layout (pls refer to the figure attached),

NMOS

one prominent advantage of this type of transistor is it makes the layout quite compact for very large ratio of L/W.
I just wonder, whether it has other advantages and its disvantages.

Thanks

 

[erikl]

Looks much more like a silicided nplus diffusion resistor (below POLY1).

 

[abonic]

Looks much more like a silicided nplus diffusion resistor (below POLY1).

Quite like;-)
Actually it is a N-Ch MOSFET

 

[dick_freebird]

Every serpentine resistor -is- a field MOS device (just
poorly engineered, if at all). The "DIFF" (I'd presume this
is "active area" / "thin ox") is not continuous across the
folds and any "gate" between the serpentine folds is
field, not thin ox in this case - a field FET. I believe
the only function of the poly here is as a field plate
(probably to keep said parasitic FETs out of play).

 

[cmos_ajay]

This snake layout will have more parasitic capacitance than a common centroid or interdigitated layout.

 

[abonic]

dear dick,
I have no idea of what the "gate" between the serpentine folds actually is.
It seems this structure only increases the parasitic MOS/Cap just as ajay said.

 

[berkeleyanalog]

There is no gate contact, anyway. This is not a transistor.

 

[Dominik Przyborowski]

You can make very long and narrow mosfet in this snake shape, but it has only sense if this mosfet is used as large value resistor - no matching, speed, etc. advantages over rectangular, ELT or diamond layout style.

 

[rangermad]

I've used this style of layout for weak pull up/pull down transistors. That is about the only use for it.

 

[abonic]

Pcell does not have gate contact typically, you have to add it in your layout

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I've used this style of layout for weak pull up/pull down transistors. That is about the only use for it.

Pretty reasonable