Polishing pads having a foundation layer and a window attached to the foundation layer, and methods of fabricating such polishing pads, are described. In an example, a polishing pad for polishing a substrate includes a foundation layer having a first modulus. A polishing layer is attached to the foundation layer and has a second modulus less than the first modulus. A first opening is through the polishing layer and a second opening is through the foundation layer. The first opening exposes at least a portion of the second opening and exposes a portion of the foundation layer. A window is disposed in the first opening and is attached to the exposed portion of the foundation layer.