In this paper we propose a utilization of infinite RRC-pulses (with finite root raised cosine spectrum) as shapes for subcarriers' spectrums in spectrally efficient frequency division multiplexing (SEFDM). For this purpose, we suggest algorithms for SEFDM generation and detection in frequency domain. Employing the dualism of Fourier transforms, we treat spectrum samples as time-domain samples, and entire SEFDM spectrum is considered as a time-domain faster-than-Nyquist signal. This approach allows a signal detection based on the Viterbi algorithm. The computational complexity of this receiver depends linearly on a number of allocated subcarriers. A transition from sine to RRC subcarriers' spectrums leads to increase of SEFDM symbol duration in time domain. We have demonstrated by simulation that bandwidth and energy consumptions of SEFDM with RRC subcarriers' spectrums are significantly lower than the consumptions of SEFDM with sine subcarriers' spectrums under a fixed computational complexity of the receiver. In addition, we have represented the comparison of our signals with the conventional SEFDM in terms of modified energy consumptions taking a signal peak to average power ratio into account. In this case, SEFDM with RRC subcarriers' spectrums also outperform SEFDM with sine subcarriers' spectrums.