A fuzz pedal, when silicon v. germanium is brought up, almost always refers to a "Fuzz Face" circuit. This is an extremely simple circuit, with no input buffer, two transistors, a few capacitors and, I think, 5 resistors. There's also to potentiometers.
Silicon v. germanium in this refers to the type of transistors used. Germanium transistors pre-date silicon transistors, and in most respects are completely inferior to silicon. They vary widely in electrical properties, change properties as the temperature changes, leak (meaning current flows when there's no input signal), they've got low gain and wretched slew rates (how well they change directions to follow the input wave). They're totally crappy for computing and high fidelity applications, which is why they are no longer manufactured and have been replaced by silicon.
But in fuzz face circuits, they are magic. Germanium FF's have a really nice soft fuzziness to them that's really musical. By contrast, silicon FF's tend to be harsh and buzzy - kind of an "ice pick in the forehead" type of sound. There are a few models of silicon transistor that have a sufficently low gain to be a better fit in a fuzz face, but still don't sound as good as germanium transistors.
However, as germanium transistors of the same model vary like crazy, a FF circuit has to be custom tailored to each pair of transistors used. In addition, the transistors have to be selected to be a good match for each other by measuring the gain of each transistor and pairing them up accordingly. Once the transistors are tested and matched up, the resistor values in the FF circuit need to be adjusted to match the specific gains of the transistors in order to get the best sound out of the stompbox.