In this study, a metal-insulator-semiconductor (MIS) type Schottky barrier diodes (SBDs) were fabricated by growing a thin Al2O3 insulator layer between Au/Ti and n-GaAs using atomic layer deposition (ALD) method. The effect of temperature and voltage on interface states (N-ss) and series resistance (R-s) of the (Au/Ti)/Al2O3/n-GaAs (MIS) type Schottky barrier diodes (SBDs) was investigated using the capacitance/conductance-voltage (C/ (G/omega-V) data measured in wide range of temperature (200-380 K) and voltage (+/- 5 V). It was found that C and G/omega are strongly dependent on temperature and voltage. The value of C in the forward bias region reaches to maximum and then becomes negative. This negative capacitance (NC) behavior of this SBD is observed for each temperature level. Also, capacitance-current (C-I) and conductance-current (G/omega-I) plots were drawn to explain the NC behavior. The negative value of C in the accumulation region corresponds to the maximum value of G/omega. Such behavior of C can be explained by the loss of interface charges located at (Al2O3)/n-GaAs interface because of impact ionization process, the existence of surface states (N-ss), series resistance (R-s) and interfacial of (Al2O3) oxide layer.Therefore, the voltage dependent profiles of R-s and N-ss were obtained using Nicollian-Brews and Hill-Colleman methods for enough high forward biases as a function of temperature at various positive bias voltages. The changes in R-s and N-ss values were attributed to restructure and reordering of the carriers under temperature and voltage effects.