Is there such thing as a PWM Transistor?
A PWM with 0% period should be completely off, no spikes. A simple ADC could help with PWM to Digital.

The problem is that while your RC receiver says it's just PWM, it is not. It's a specific protocol that works slightly different. Essentially, it is a PWM signal with 1ms to 2ms pulses at 50hz. A centered pulse is neutral. Even with a push button and not an analog stick, the protocol stays the same.

I highly doubt there is a transistor that does what you want, you would need a custom design or a microcontroller to do what you want. Simple enough to do, read an analog input, determine what the pulse length is, and output to a digital pin the state.

This question is about reverse engineering a product that does just that:
Nano Electric Receiver Switch - Circuit Components
You may want to read it hint hint