Control of the shape of features during etching or deposition is central to the success of many plasma processes used for semiconductor manufacturing. Unfortunately, current models of feature shape evolution are relatively primitive with limited predictive capability. A major goal of plasma process modeling is to develop truly predictive feature shape evolution simulations. One reason for the difficulties experienced in developing predictive shape evolution models is that many parts of the plasma play a role. Events at the tool scale help to govern the composition, flux and energy of ionic and neutral species that impact substrates. The sheath and local presheath above the substrate play important roles in governing positive ion energy and angular distributions at surfaces. In some cases, electron energy distributions and negative ions can be important in feature differential charging phenomena. Features are themselves often complex, with materials and geometries that challenge current models. Processes within a feature, including neutral reaction, ion-sidewall scattering, sputtering, charge transport and redeposition of etch products are all potentially important. An important issue is the sensitivity of the predicted shape evolution to inaccuracies in various parts of the model. In this talk, I will review the progress in developing models of reactive plasma processes, focusing on the phenomena that are known or suspected to affect feature shape evolution. Predictive feature shape evolution models must include the tool scale, the sheath, the feature itself, as well as processes occurring at surfaces. I will review progress made in using vacuum beam experiments, atomistic simulations, and plasma experiments that focus on feature shape evolution. I will highlight the need for more systematic studies of plasma process feature shape evolution, the development of novel sensors, and the development of physically-based, phenomenological surface rate expressions.