Horizontal or vertical Poly

hello,
First of all thanks for such a useful site!!!!

Today a question came to my mind that why Poly in 22 nm technology is only vertical , but in earlier technology it may be horizontal or vertical ..

Please anybody clarify my doubt..

It is not only for 22nm and not only vertical, it depends on fab/process. There are processes which use only horizontal gates as well as only vertical gates, previous nodes like 28/32nm also use fixed orientation. Usually the orientation requirements apply only for low voltage transistors and high voltage could be placed as you want (but not in every process). But I saw the process where low voltage transistors have to be vertical and high voltage have to be horizontal. These requirements are introduced due to process control, to achieve good yield, I think.

Hi EmilioSergio,

Thanks for the explanation...
Can you please elaborate on "process control, to achieve good yield" regarding to the question which I asked..

I meant that if all gates have the same orientation, some fabrication steps do not need to be so strictly controlled to avoid gate shapes/thickness variation causing circuit malfunctions (which is important for very small length and small oxide/gate poly/gate metal thickenss). Probably it allows to remove some costs. But it is only my theory for this conjuncture (based on my knowledge of some effects existing for semiconductor manufacturing). Also it can be connected with transistors characteristics, which are different for different orientation, due to silicon crystal structure. I think there could be a lot of other effects causing fixed gate orientation requirements. Exact explanation you could get from people from fabs, who take care of front end process steps, but I think nobody will share this since these are company secrets.