Scalability and the absence of moving components are excellent advantages for integrated thermoelectric (TE) devices in microelectronic applications. Both TE coolers (TECs) and TE generators (TEGs) could enhance computer chip efficiency and reliability. We show the fabrication of CMOS-compatible silicon–germanium (SiGe)based TEC and TEG multistage structures for lateral temperature gradients with microelectronic manufacturing processes on 300-mm wafers. The smallest structures have a size of 1500 × 500 nm and achieved a cooling temperature difference of around 0.13 K. The TEGs of equal dimensions reached a maximum voltage factor of 545 mV·mm⁻²·K⁻¹ and a specific power generation factor of 2.1 nW·mm⁻²·K⁻² near room temperature. Three different n-type SiGe materials were compared and examined regarding their TE properties. To address the challenge of contacting the TE element, we have captured and analyzed transmission electron microscopy (TEM) images for defect identification.