Logic gates are physical semiconductor devices, made using diodes and transistors and sometimes, resistors (this needs to be clarified). However, the representations aren't.
Edit: I don't know much about the logic technologies used nowadays. From what I've Googled, TTL is actually faster (the ECL configuration is even faster) than CMOS (possibly due to the fact that it doesn't pose that much of capacitive reactance at high frequencies) but it consumes more power, while the CMOS logic consumes lesser power as the only one contributing to the power intake is the capacitive transient at the start, which is pretty small for low frequencies. Also, MOSFETs can deliver more output power than BJTs. But they're not so suitable for high-speed applications because of its Gate-Source capacitance. Moreover, CMOS is more expensive than TTL logic.