µs ? You ask for an increase of factor 1000:) . I'm shure you looked up the common analog semiconductor companies.... however have you contacted them , or some distributors ?
In the rare conditions you need some fF resolutions in some µs you can't expect ready made ICs for it. (application?market?)
Build a LC oscillator in the xxMHz range and use (heterodyne) P/F demodulation?
Greetings from Germany
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