I want to plot using RegionPlot3D the following region:

That is, the half circle in the positive x half plane, of radius 2, at "height" z=1.

How can I do that?

I tried this command:

RegionPlot3D[0 < x < Sqrt[1 - y^2] && z == 1, {x, -1.2, 1.2}, {y, -1.2, 1.2}, {z, 0, 1.2}]

But this is incorrect and gives me an error.

Is that possible at all using RegionPlot3D together with a collection of predicates?

I guess one can obtain this output graphics with SliceContourPlot3D or ParametricPlot3D, but I want to check for the possibility with RegionPlot3D.