In Star Trek II: The Wrath of Khan, the planet-terraforming device is called the Genesis Device.
The device is developed by Carol Marcus and her research team at the Regula I space station. Its purpose is to transform a lifeless world into one capable of supporting life, using a process called “proto-matter” technology. The film presents Genesis as both a scientific breakthrough and a potential weapon.
Khan Noonien Singh steals the device after attacking Regula I, hoping to use it against Captain Kirk. Kirk later activates it aboard the USS Reliant during the climactic battle, destroying the ship and creating the Genesis Planet.
The Genesis Device is sometimes confused with the Genesis Planet, but they are different: the device is the technology, while the planet is the world created by it. The device also drives the plot of Star Trek III: The Search for Spock.