About fabrication process

[adityavoora]

Why gate is fabricated before diffusion fabrication ??

 

[kenambo]

To avoid source and drain mismatch.. this technique is called self aligned gate..
By fabricating Gate first.. when you do diffusion the source and drain regions are aligned with respect to drain/source of that MOS.

Please Refer CMOS circuit design layout and simulation by Jacob Baker page No 86.

Thanks