The invention relates to a semiconductor sensor device (10) for sensing a substance comprising at least one mesa- shaped semiconductor region (11) which is formed on a surface of a semiconductor body (12) and which is connected at a first end to a first electrically conducting connection region (13) and at a second end to a second electrically conducting connection region (14) while a fluid (20) comprising a substance (30) to be sensed can flow along the mesa- shaped semiconductor region (11) and the substance (30) to be sensed can influence the electrical properties of the mesa-shaped semiconductor region (11), wherein the mesa-shaped semiconductor region (11) comprises viewed in a longitudinal direction subsequently a first semiconductor subregion (1) comprising a first semiconductor material and a second semiconductor subregion (2); comprising a second semiconductor material different from the first semiconductor material. According to the invention the first semiconductor material comprises a IV element material and the second semiconductor material comprises a III-V compound. Due to difference in surface chemistry between subregions 1,2 a substance (30) like an antibody to which a protein signaling a disease can be bonded can be more selectively attached to the desired first region (1)
