switch schematic and simulation
You are trying to switch on and off a signal passed through a transmission gate (aka analogue switch). Your output is not connected to anything so here's a problem - even if the analogue switch open-circuited up to 100 Mohms, you would still see a signal at the output.

MOSFETs have a finite open-circuit impedance of a few Mohms at best and, they also have quite high drain-source capacitance so you are bound to get some leak-through of the signal when the gate is off.

Try loading the output with 1 kohm and see what happens.