In this paper, we have proposed a exp(-Phi(xi) method to establish hyperbolic, trigonometric and rational function solutions for fractional differential equations in the sense of modified Riemann-Liouville derivative. To illustrate the validity of this method, we solve the time-fractional Sharma-Tasso-Olver and (3 + 1)-dimensional time fractional Korteweg-deVries-Zakharov-Kuznetsov (KdV-ZK) equations. This type of method will be newly submitted to literature to construct exact solutions of nonlinear fractional differential equations (NFDEs). (C) 2016 Elsevier GmbH. All rights reserved.