Electrostatic force microscopy and scanning gate microscopy are employed to investigate the local electrical characteristics of single-walled carbon nanotube (SWCNT) devices that are fabricated by alternating current dielectrophoresis with high spatial resolutions. The results show good electrical anchoring of nanotubes to electrodes and absence of local gate dependence as well as global gate dependence while device resistance can be dominated by contact resistances among bundles of SWCNTs.