a semiconductor device having a test mark comprising : a semiconductor substrate ; a first teos layer formed on the semiconductor substrate ; a second teos layer formed on the first teos layer and having a fluidity lower than that of the first teos layer at an elevated temperature ; a recess formed in the first and second teos layers and exposing the surface of the semiconductor substrate , wherein the horizontal cross section of the recess is substantially rectangular in configuration ; and a metal layer formed between the first and second teos layers and opposing to the corner of the recess .