In order to see the effect of interfacial layer on electrical characteristics both Au/n-4H-SiC (MS) and Au/TiO2/n-4H-SiC (MIS) type Schottky barrier diodes (SBDs) were fabricated and their main electrical parameters were investigated by using the forward and reverse bias current-voltage (I - V), capacitance/conductance-voltage (C/G-V) measurements at room temperature. The ideality factor (n), series and shunt resistances (R-s, R-sh), barrier height (BH), depletion layer width (W-D) and the concentration of donor atoms (N-D) were obtained before and after illumination. The energy density distribution profile of surface states (N-ss) was also obtained by taking into account voltage dependent effective BH (Phi(e)) and ideality factor (n(V)). All of these experimental results confirmed that the use of a high dielectric material or insulator layer (TiO2) between metal and semiconductor leads to improvements in the diode performance in terms of Rs, Rsh, BH, Nss and rectifier rate (RR = I-F / I-R for sufficiently high forward and reverse current). Another important result is the negative capacitance (NC) behavior observed in the forward bias C - V plot for the Au/n-4H-SiC (MS) diode, but it disappears in Au/TiO2/n-4H-SiC (MIS) diode and also the minimum value of C - V plot corresponds to maximum value of G/omega - V plot in the accumulation region. Such behavior of NC shows that the material displays an inductive behavior.