An integrated optical device having at least two optical devices integrated therein and a method of fabricating the integrated optical device are provided. To fabricate an integrated optical device having optically connected and electrically isolated first and second optical devices on a substrate of a first conductive type, an active layer and a clad layer of a second conductive type are first formed in a mesa structure on the substrate, an SI clad layer is then formed on the substrate surrounding the clad layer of the second conductive type and the active layer, and finally first and second conductive layers are formed into trenches by diffusing a dopant of the second conductive type into the SI clad layer in areas corresponding to the first and second optical devices.