Ecumenopolization is the term and action of the form of colonization that turns a celestial body, usually a planet or moon, into an Ecumenopolis, which in turn is a city that stretches across the entire celestial body it is located on.
This form of colonization is most typically used on S-Class, I-Class, and D-Class worlds as they (typically) do not have life on them for this process to endanger.
Materials used in the process of Ecumenoplization are mined from either the celestial body in question, or neighboring bodies such as planets, moons, and asteroids. Though those who are looking to turn a celestial body into an Ecumenopolis may use other sources.
Usually this process will begin with the construction of a large dome-like structure that creates an artificial atmosphere with the required or wanted specifications needed for that particular species looking to colonize said body. This isn't always the case as they may not need this to survive.
Due to the process being rather expensive on both resources, or funds if the particular civilization uses currency, this process is usually not used. Instead, terraforming is favored over it however this isn't always the case as a celestial body may lack the requirements to be terraformed in the way the would be colonizer needs it to be.