We performed scanning tunneling microscopy (STM) experiments on layered semiconductor compound surfaces which suggest a significant influence of electrostatic forces (EF) on the imaging process. We performed STM experiments at varying tunneling biases on plain MoTe2 and ultrathin epitaxial WS2 films on MoTe2 substrates. We observed tunneling bias dependent height changes of up to several nanometers of layer edges and layer terraces. Both of the samples showed height increases of up to 8 nm for step edges depending on the tunneling bias. Only at certain biases the values known from X-ray diffraction for the layer thickness were approached. These observations cannot be explained solely by electronic effects and tunneling probability changes. Our evaluation of the results shows that mechanical changes of the morphology caused by varying EF interaction between tip and sample are likely to be the cause of these phenomena. In order to investigate the magnitude and influence of EF between tip and sample more closely we performed additional experiments with bias applied atomic force microscopy (BAAFM) which indicate a strong influence of EF on the imaging process. Atomic force curves with additionally applied bias yielded that the EF are in the range of several ten to several hundred nN depending on the tunneling bias. The corresponding charge density on tip and sample suggests the presence off single electrons and holes at the interface instead of homogeneous charge densities which might result in a pulsed EF interaction between tip and sample.