Method for fabricating a semiconductor structure. The method includes: providing a crystalline silicon substrate; defining an opening in a dielectric layer on the crystalline silicon substrate, the opening having sidewalls and a bottom wherein the bottom corresponds to a surface of the crystalline silicon substrate; providing a confinement structure above the dielectric layer, thereby forming a confinement region between the confinement structure and the dielectric layer; and growing a crystalline compound semiconductor material in the confinement region thereby at least partially filling the confinement region. The present invention also provides an improved compound semiconductor structure and a device for fabricating such semiconductor structure.