This study aims to provide a semantic-syntactic approach to the clitic climbing phenomenon in which clitics of an embedded infinite verb appear attached to the main verb. Following the concept of types of features and feature valuation suggested by Pesetsky & Torrego (2007), I assume that the head C of CP can have either uninterpretable valued T feature or uninterpretable unvalued T feature. I propose that CP phase of the subordinate clause can be expanded to vP phase of the matrix clause when the main verb selects C with uninterpretable unvalued T feature and the phase extension can be applied to the clitic climbing constructions. Therefore, I argue that clitic climbing is related to the feature valuation of C and the possibility of phase extension of subordinate clause according to main verbs that subcategorize it, such as volitional verb, factive-emotive verb, epistemic verb, etc. Furthermore, I claim that a binding domain of the embedded clause provides evidence of this syntactic process of phase extension.