Many problems exist in current photoresist designs that will limit their ability to obtain the performance required for future generations of integrated circuit devices. In order to overcome these challenges, novel resist designs are required, along with advancement in the fundamental understanding of the source of these problems. A mesoscale kinetic Monte Carlo simulation of resists was developed to probe the effects of changes in resist formulation and processing. A detailed SEM simulator was developed in order to better understand the effect of metrology on the characterization of the final resist relief image. Several important structure-property relations were developed for the prediction of glass transition temperature in molecular resists and the prediction of the solubility of molecular resists in developer. Five new families of molecular resists were developed that provide solutions to some of the limitations in current resist designs. Single component molecular resists have all of the functional groups required to act as a chemically amplified resist contained in a single molecule. This eliminates inhomogeneities in the resist and provides improved line edge roughness. Non-chemically amplified molecular resists were developed that have very good sensitivity due to the unique dissolution properties of molecular resists. Negative tone molecular resists were developed that have an excellent combination of resolution, sensitivity, and line edge roughness with better resolution than has been previously seen in negative tone resists. Control methods were also developed to improve the resolution of these types of negative tone resists even further.