It is possible for this shape to tile the infinite plane, if copies of the shape are rotated 45, 135, 225 and 315 degrees from the original. You can then overlay a unit square grid which neatly lines up with the shape as below:

Translating this back to the original shape, this corresponds to drawing lines from the centre of the semicircle to each of the 90 degree corners, dissecting the shape into two isosceles triangles and a dart shape. Not only is this a dissection in only three pieces, but it can be hinged as well, a la Henry Dudeney.