PowerPoint provides so many basic shapes within the Shapes gallery. All of these shapes can be used in many ways, and that in itself works most of the time. Yet there are plenty of other shapes that are not provided within the Shapes gallery but you can easily modify an existing shape a wee bit to end up with something you need. A semi-circle is a perfect example of such a shape.
To learn more, choose your version of PowerPoint. If we do not have a tutorial for your version of PowerPoint, explore the version closest to the one you use.