Single-wall carbon nanotubes (SWNTs) are promising building blocks for the fabrication of nanoelectronic devices. However, achieving control over their assembly on substrates has been challenging and is still a bottleneck to their utilization. Herein, we present a general method for directing the chemical assembly of SWNTs on substrates through electrostatic interactions. By covalently functionalizing both the nanotube sidewalls and the SiO(2) substrate with charged groups, dense networks of SWNTs were produced. The method is selective and highly efficient to process network field-effect transistors.