Doctor of Philosophy in Engineering can be done in conjunction with a PhD (for the MS/PhD option) or alone. Degrees are granted after completion of programs of study that emphasize the application of the natural sciences to the analysis and solution of engineering problems. Advanced courses in mathematics, chemistry, physics, and the life sciences are normally included in a program that incorporates the engineering systems approach for analysis of problems. Students must have a bachelors degree in one of the accredited engineering curricula or satisfy the equivalent of a bachelors degree in engineering as determined by the department concerned for admission to this program.
For more information, please see http://me.berkeley.edu/graduate-student-handbook/71-phd-degree-requirements. A printable version of the curriculum can be found here.