Kind of ... The boost that a Turbocharger delivers is dependant not only on engine speed, but also on how much fuel you're burning - if you start climbing a hill and put your foot down to maintain speed then more fuel is burnt and the turbo boost increases without any increase in engine speed.

A supercharger, on the other hand, delivers a fixed amount of air per revolution of the engine regardless of how much fuel you're burning - this presents difficulties: It places a hard limit on how much fuel you can burn (because you can only burn as much fuel as you have oxygen to burn it with), this is especially important at high altitudes when you need to force larger volumes into the engine to get the required mass of air for combustion.

There are in 2-stoke diesels (EMD 645, for example) that have supercharged variants for low altitude use, and turbocharged variants for high-altitude/more demanding purposes. However, because 2-stoke engines need forced induction to work* a standard turbo is unsuitable at idle/low power since it wouldn't deliver the intake pressure required for the engine to run at all. To cope with this the turbo is driven from the crankshaft through a clutch that allows it operate (effectively) as a supercharger at low speeds but as full turbo at high speed.

* In case you're wondering: on a small 2-stroke petrol engine such as might be found on a chainsaw or motorcycle, forced induction is achieved by using the crankcase to pressurise the charge - so the charge is sucked into the crankcase through a non-return valve during the compression stroke then pressurised during the power stroke before flowing into the cylinder through the intake port.