Availability of 0.01 pF and 1 pF chip capacitor with SRF more than 15 GHz
You are talking about so small capacitances that you don't need any discretes to achieve them. According to [1] the capacitance of an 1206-size components pad is about 0.72 pF. Therefore there is no point in creating discrete capacitors smaller than about 10 pF because it is easier to embed them into the PCB and you get smaller parasitics too [2]. 

The second reference I used talks about some fancy dedicated PCB materials for embedded capacitors, but you can also use regular FR4 PCBs. Howevere, you are most probably going to need impedance control. Calculators and equations for PCB embedded capacitors are readily available by googling i.e. http://chemandy.com/calculators/rectangular-capacitor-calculator.htm.

[1] http://www.sigcon.com/Pubs/edn/parasiticpads.htm

[2] https://multimedia.3m.com/mws/media/251029O/fabrication-of-embedded-capacitance-printed-circuit-boards.pdf