Hi @Tim Edwards which cap in pdk would be suitable for high speed operations in Few GHz? Any idea pls. I need it as decoupling cap for dc bias isolation

Any linear cap is fine, so either the MiM caps or the VPP (MoM) caps is good.

sure, I think the direction does not matter? how do we know which side is m3 and m4 from symbol 😅, a silly question

Of course the cap is not "polarized" but the rounded edge indicates the capacitor bottom, which is useful to know if you are trying to carefully control parasitics. For MiM caps, the general rule is to always contact both cap plates from above so as to avoid turning the capacitor into a large antenna during manufacturing, which can damage the capacitor. SkyWater does not have any such rule, so I mention it as an advisory because other foundries do have such a rule and enforce it through DRC.

@Tim Edwards this looks like a good idea to form rram while in factory. maybe thats why some of the rram cells I got in chip were already formed?