An integrated circuit package is proposed in which a laminar substrate 41 is provided with an aperture 43. A heat-spreader member 1 is mounted to cover this aperture 43, and contains a cavity 3 opening towards the aperture 43 in the substrate 41. A stack of integrated circuit circuits 11, 21, are located with one integrated circuit 21 of the stack inserted into the cavity 3, and one integrated circuit 11 of the stack electrically connected to the substrate 41.