Q:

How do I create a solid semi circle shape in Photoshop? 

Like this:

Thank you very much,

A:

Step 1: Open a new document.  Create a New Layer.  Select Marquee Tool.  Press Shift and Draw a circle.  Alt + Delete and color fill the layer. 
Step 2: Double click on the layer.  Select Stroke - Select color and size of the border as per your requirement. 
Step 3: Ctrl + J to duplicate the layer. 
Step 4: Ctrl+T and reduce the size of the circle. 
Step 5: Ctrl + Select the small circle layer.  Once the small circle is selected, click the big circle layer and delete
Step 6: Deselect the selection and hide the small circle layer. 
Step 7: Select Rectangular marquee tool.  Create a rectangle and delete the selection.  Your semi circle is ready.