PURPOSE: To provide an element which can control the atom arrangement so as to get the optimum light emitting efficiency and thereby exhibits the same characteristic at all times by making the device in such a structure that Ge atoms in an SiGe compound alloy system layer may be arranged in layers perpendicular to an interface and excited electrons may be confined in a quantum well.

CONSTITUTION: An Si layer 102, an SiGe compound alloy system layer 103, and an Si layer 104 constitute a quantum well structure. In this structure, the Ge atom concentration in the SiGe layer is so determined that the level at the top of the valence band of the SiGe layer may be higher than the level at the top of the valence band of the Si layer and the level at the bottom of the valence band of the Side layer may be lower than the level at the bottom of the valence band of the Si layer and no bonding of Ge atoms themselves may occur. Therefore, a confinement effect of excited electrons or holes is increased and thereby a light emitting efficiency is enhanced. When the SiGe layer has a deformed crystal structure or an asynchronous structure, the light emitting efficiency becomes higher. A substrate 101 is made of silicon, but it is acceptable to form a quantum well structure on a device on the Si substrate or on an interconnect.