We studied the buried growth of a GaAs layer over a tungsten stripe using organometallic vapor-phase epitaxy. Triethylgallium (TEG) and trimethylgallium (TMG) were used as group III sources. For growth without polycrystal-like deposition on tungsten surface, the required growth temperature using TMG was lower than that using TEG. For 2-mum-thick growth over a 1-mum-wide tungsten stripe, the flatness of the surface grown using TMG was better than that using TEG. Therefore, the migration length of TMG on tungsten and GaAs must be longer than that of TEG. For a heterojunction bipolar transistor with a tungsten stripe as the collector electrode, a 70-nm-wide tungsten stripe was buried under a 0.77-mum-thick layer of GaAs with a flat surface using TMG. A current gain of 4 was measured although the active region was grown over tungsten stripe.